Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$116.92	8.235%	$126.5484	$126.55	$126.55	$126.50
Purchase #2	$149.38	4.514%	$156.123	$156.12	$156.10	$156.10
Purchase #3	$147.30	8.841%	$160.3228	$160.32	$160.30	$160.30
Purchase #4	$158.95	4.156%	$165.556	$165.56	$165.55	$165.60
Purchase #5	$163.85	6.386%	$174.3135	$174.31	$174.30	$174.30
Purchase #6	$240.83	11.459%	$268.4267	$268.43	$268.45	$268.40
Purchase #7	$119.55	10.346%	$131.9186	$131.92	$131.90	$131.90
7 purchase totals =	$1,096.78		$1,183.2090	$1,183.21	$1,183.15	$1,183.10