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	$113.25	8.546%	$122.9283	$122.93	$122.95	$122.90
Purchase #2	$46.89	13.596%	$53.2652	$53.27	$53.25	$53.30
Purchase #3	$115.25	7.543%	$123.9433	$123.94	$123.95	$123.90
Purchase #4	$197.46	12.777%	$222.6895	$222.69	$222.70	$222.70
Purchase #5	$79.81	8.278%	$86.4167	$86.42	$86.40	$86.40
Purchase #6	$99.51	5.657%	$105.1393	$105.14	$105.15	$105.10
Purchase #7	$202.30	7.362%	$217.1933	$217.19	$217.20	$217.20
7 purchase totals =	$854.47		$931.5756	$931.58	$931.60	$931.50