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	$152.55	6.410%	$162.3285	$162.33	$162.35	$162.30
Purchase #2	$67.72	7.393%	$72.7265	$72.73	$72.75	$72.70
Purchase #3	$146.33	9.176%	$159.7572	$159.76	$159.75	$159.80
Purchase #4	$230.90	12.232%	$259.1437	$259.14	$259.15	$259.10
Purchase #5	$53.81	12.627%	$60.6046	$60.60	$60.60	$60.60
Purchase #6	$223.34	12.256%	$250.7126	$250.71	$250.70	$250.70
Purchase #7	$85.36	12.801%	$96.2869	$96.29	$96.30	$96.30
7 purchase totals =	$960.01		$1,061.5600	$1,061.56	$1,061.60	$1,061.50