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	$188.33	3.268%	$194.4846	$194.48	$194.50	$194.50
Purchase #2	$149.78	13.641%	$170.2115	$170.21	$170.20	$170.20
Purchase #3	$99.62	8.753%	$108.3397	$108.34	$108.35	$108.30
Purchase #4	$174.83	11.159%	$194.3393	$194.34	$194.35	$194.30
Purchase #5	$166.33	7.557%	$178.8996	$178.90	$178.90	$178.90
Purchase #6	$77.31	6.126%	$82.046	$82.05	$82.05	$82.00
Purchase #7	$181.82	8.127%	$196.5965	$196.60	$196.60	$196.60
7 purchase totals =	$1,038.02		$1,124.9172	$1,124.92	$1,124.95	$1,124.80