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	$70.44	10.820%	$78.0616	$78.06	$78.05	$78.10
Purchase #2	$87.44	9.474%	$95.7241	$95.72	$95.70	$95.70
Purchase #3	$216.36	3.142%	$223.158	$223.16	$223.15	$223.20
Purchase #4	$100.30	4.815%	$105.1294	$105.13	$105.15	$105.10
Purchase #5	$237.54	5.646%	$250.9515	$250.95	$250.95	$251.00
Purchase #6	$25.26	13.474%	$28.6635	$28.66	$28.65	$28.70
Purchase #7	$84.97	8.722%	$92.3811	$92.38	$92.40	$92.40
7 purchase totals =	$822.31		$874.0692	$874.06	$874.05	$874.20