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	$173.86	13.109%	$196.6513	$196.65	$196.65	$196.70
Purchase #2	$50.92	11.464%	$56.7575	$56.76	$56.75	$56.80
Purchase #3	$153.77	11.549%	$171.5289	$171.53	$171.55	$171.50
Purchase #4	$133.70	11.705%	$149.3496	$149.35	$149.35	$149.30
Purchase #5	$185.83	13.696%	$211.2813	$211.28	$211.30	$211.30
Purchase #6	$62.58	11.769%	$69.945	$69.95	$69.95	$69.90
Purchase #7	$50.59	7.652%	$54.4611	$54.46	$54.45	$54.50
7 purchase totals =	$811.25		$909.9747	$909.98	$910.00	$910.00