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	$89.56	7.557%	$96.328	$96.33	$96.35	$96.30
Purchase #2	$134.42	13.115%	$152.0492	$152.05	$152.05	$152.00
Purchase #3	$60.53	3.271%	$62.5099	$62.51	$62.50	$62.50
Purchase #4	$200.47	5.718%	$211.9329	$211.93	$211.95	$211.90
Purchase #5	$235.47	7.442%	$252.9937	$252.99	$253.00	$253.00
Purchase #6	$37.51	7.805%	$40.4377	$40.44	$40.45	$40.40
Purchase #7	$237.64	13.839%	$270.527	$270.53	$270.55	$270.50
7 purchase totals =	$995.60		$1,086.7784	$1,086.78	$1,086.85	$1,086.60