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	$156.61	9.739%	$171.8622	$171.86	$171.85	$171.90
Purchase #2	$53.57	5.783%	$56.668	$56.67	$56.65	$56.70
Purchase #3	$179.87	5.146%	$189.1261	$189.13	$189.15	$189.10
Purchase #4	$83.86	7.208%	$89.9046	$89.90	$89.90	$89.90
Purchase #5	$54.37	6.210%	$57.7464	$57.75	$57.75	$57.70
Purchase #6	$138.96	8.744%	$151.1107	$151.11	$151.10	$151.10
Purchase #7	$229.74	5.304%	$241.9254	$241.93	$241.95	$241.90
7 purchase totals =	$896.98		$958.3434	$958.35	$958.35	$958.30