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	$165.75	9.415%	$181.3554	$181.36	$181.35	$181.40
Purchase #2	$181.83	6.648%	$193.9181	$193.92	$193.90	$193.90
Purchase #3	$60.72	10.164%	$66.8916	$66.89	$66.90	$66.90
Purchase #4	$126.34	4.710%	$132.2906	$132.29	$132.30	$132.30
Purchase #5	$233.56	8.283%	$252.9058	$252.91	$252.90	$252.90
Purchase #6	$154.84	4.843%	$162.3389	$162.34	$162.35	$162.30
Purchase #7	$106.56	4.384%	$111.2316	$111.23	$111.25	$111.20
7 purchase totals =	$1,029.60		$1,100.9320	$1,100.94	$1,100.95	$1,100.90