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	$183.36	7.328%	$196.7966	$196.80	$196.80	$196.80
Purchase #2	$153.93	5.814%	$162.8795	$162.88	$162.90	$162.90
Purchase #3	$141.92	5.523%	$149.7582	$149.76	$149.75	$149.80
Purchase #4	$247.62	9.283%	$270.6066	$270.61	$270.60	$270.60
Purchase #5	$29.98	10.589%	$33.1546	$33.15	$33.15	$33.20
Purchase #6	$90.39	11.383%	$100.6791	$100.68	$100.70	$100.70
Purchase #7	$137.48	12.342%	$154.4478	$154.45	$154.45	$154.40
7 purchase totals =	$984.68		$1,068.3224	$1,068.33	$1,068.35	$1,068.40