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	$212.31	5.384%	$223.7408	$223.74	$223.75	$223.70
Purchase #2	$111.91	13.869%	$127.4308	$127.43	$127.45	$127.40
Purchase #3	$212.93	5.793%	$225.265	$225.27	$225.25	$225.30
Purchase #4	$149.42	6.686%	$159.4102	$159.41	$159.40	$159.40
Purchase #5	$67.67	6.410%	$72.0076	$72.01	$72.00	$72.00
Purchase #6	$80.40	13.113%	$90.9429	$90.94	$90.95	$90.90
Purchase #7	$210.82	8.684%	$229.1276	$229.13	$229.15	$229.10
7 purchase totals =	$1,045.46		$1,127.9249	$1,127.93	$1,127.95	$1,127.80