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	$112.78	10.821%	$124.9839	$124.98	$125.00	$125.00
Purchase #2	$61.49	9.118%	$67.0967	$67.10	$67.10	$67.10
Purchase #3	$225.85	10.503%	$249.571	$249.57	$249.55	$249.60
Purchase #4	$179.45	11.485%	$200.0598	$200.06	$200.05	$200.10
Purchase #5	$176.39	4.363%	$184.0859	$184.09	$184.10	$184.10
Purchase #6	$87.90	12.836%	$99.1828	$99.18	$99.20	$99.20
Purchase #7	$141.76	12.583%	$159.5977	$159.60	$159.60	$159.60
7 purchase totals =	$985.62		$1,084.5778	$1,084.58	$1,084.60	$1,084.70