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	$149.73	11.525%	$166.9864	$166.99	$167.00	$167.00
Purchase #2	$147.33	7.604%	$158.533	$158.53	$158.55	$158.50
Purchase #3	$89.82	7.110%	$96.2062	$96.21	$96.20	$96.20
Purchase #4	$168.90	3.756%	$175.2439	$175.24	$175.25	$175.20
Purchase #5	$90.73	7.626%	$97.6491	$97.65	$97.65	$97.60
Purchase #6	$89.56	12.324%	$100.5974	$100.60	$100.60	$100.60
Purchase #7	$247.89	11.146%	$275.5198	$275.52	$275.50	$275.50
7 purchase totals =	$983.96		$1,070.7358	$1,070.74	$1,070.75	$1,070.60