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	$146.64	3.242%	$151.3941	$151.39	$151.40	$151.40
Purchase #2	$239.38	12.117%	$268.3857	$268.39	$268.40	$268.40
Purchase #3	$226.84	10.307%	$250.2204	$250.22	$250.20	$250.20
Purchase #4	$77.63	5.678%	$82.0378	$82.04	$82.05	$82.00
Purchase #5	$119.28	4.508%	$124.6571	$124.66	$124.65	$124.70
Purchase #6	$152.82	9.544%	$167.4051	$167.41	$167.40	$167.40
Purchase #7	$62.59	6.661%	$66.7591	$66.76	$66.75	$66.80
7 purchase totals =	$1,025.18		$1,110.8593	$1,110.87	$1,110.85	$1,110.90