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	$97.33	7.515%	$104.6443	$104.64	$104.65	$104.60
Purchase #2	$105.37	6.757%	$112.4899	$112.49	$112.50	$112.50
Purchase #3	$234.82	5.742%	$248.3034	$248.30	$248.30	$248.30
Purchase #4	$106.71	4.703%	$111.7286	$111.73	$111.75	$111.70
Purchase #5	$66.89	6.457%	$71.2091	$71.21	$71.20	$71.20
Purchase #6	$137.77	5.447%	$145.2743	$145.27	$145.25	$145.30
Purchase #7	$230.65	8.458%	$250.1584	$250.16	$250.15	$250.20
7 purchase totals =	$979.54		$1,043.8080	$1,043.80	$1,043.80	$1,043.80