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	$89.96	10.340%	$99.2619	$99.26	$99.25	$99.30
Purchase #2	$23.48	5.605%	$24.7961	$24.80	$24.80	$24.80
Purchase #3	$238.32	10.453%	$263.2316	$263.23	$263.25	$263.20
Purchase #4	$88.51	4.746%	$92.7107	$92.71	$92.70	$92.70
Purchase #5	$70.31	3.115%	$72.5002	$72.50	$72.50	$72.50
Purchase #6	$178.31	12.629%	$200.8288	$200.83	$200.85	$200.80
Purchase #7	$170.64	12.223%	$191.4973	$191.50	$191.50	$191.50
7 purchase totals =	$859.53		$944.8266	$944.83	$944.85	$944.80