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	$97.53	13.814%	$111.0028	$111.00	$111.00	$111.00
Purchase #2	$128.87	5.118%	$135.4656	$135.47	$135.45	$135.50
Purchase #3	$54.41	9.625%	$59.647	$59.65	$59.65	$59.60
Purchase #4	$233.31	6.788%	$249.1471	$249.15	$249.15	$249.10
Purchase #5	$188.49	5.575%	$198.9983	$199.00	$199.00	$199.00
Purchase #6	$19.34	5.497%	$20.4031	$20.40	$20.40	$20.40
Purchase #7	$236.30	12.123%	$264.9466	$264.95	$264.95	$264.90
7 purchase totals =	$958.25		$1,039.6105	$1,039.62	$1,039.60	$1,039.50