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	$123.72	5.142%	$130.0817	$130.08	$130.10	$130.10
Purchase #2	$64.38	3.730%	$66.7814	$66.78	$66.80	$66.80
Purchase #3	$152.98	8.584%	$166.1118	$166.11	$166.10	$166.10
Purchase #4	$58.57	13.374%	$66.4032	$66.40	$66.40	$66.40
Purchase #5	$186.86	5.223%	$196.6197	$196.62	$196.60	$196.60
Purchase #6	$28.45	8.107%	$30.7564	$30.76	$30.75	$30.80
Purchase #7	$65.78	7.792%	$70.9056	$70.91	$70.90	$70.90
7 purchase totals =	$680.74		$727.6598	$727.66	$727.65	$727.70