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	$50.84	6.106%	$53.9443	$53.94	$53.95	$53.90
Purchase #2	$42.78	7.844%	$46.1357	$46.14	$46.15	$46.10
Purchase #3	$166.70	13.582%	$189.3412	$189.34	$189.35	$189.30
Purchase #4	$205.80	13.674%	$233.9411	$233.94	$233.95	$233.90
Purchase #5	$226.37	10.112%	$249.2605	$249.26	$249.25	$249.30
Purchase #6	$151.88	4.464%	$158.6599	$158.66	$158.65	$158.70
Purchase #7	$52.61	3.728%	$54.5713	$54.57	$54.55	$54.60
7 purchase totals =	$896.98		$985.8540	$985.85	$985.85	$985.80