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	$145.32	11.276%	$161.7063	$161.71	$161.70	$161.70
Purchase #2	$53.73	6.191%	$57.0564	$57.06	$57.05	$57.10
Purchase #3	$79.98	12.465%	$89.9495	$89.95	$89.95	$89.90
Purchase #4	$165.62	6.283%	$176.0259	$176.03	$176.05	$176.00
Purchase #5	$83.87	8.398%	$90.9134	$90.91	$90.90	$90.90
Purchase #6	$90.40	4.537%	$94.5014	$94.50	$94.50	$94.50
Purchase #7	$114.48	9.602%	$125.4724	$125.47	$125.45	$125.50
7 purchase totals =	$733.40		$795.6253	$795.63	$795.60	$795.60