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	$99.41	3.860%	$103.2472	$103.25	$103.25	$103.20
Purchase #2	$120.45	3.194%	$124.2972	$124.30	$124.30	$124.30
Purchase #3	$143.40	5.539%	$151.3429	$151.34	$151.35	$151.30
Purchase #4	$43.80	3.338%	$45.262	$45.26	$45.25	$45.30
Purchase #5	$87.70	3.131%	$90.4459	$90.45	$90.45	$90.40
Purchase #6	$58.67	6.170%	$62.2899	$62.29	$62.30	$62.30
Purchase #7	$141.59	8.289%	$153.3264	$153.33	$153.35	$153.30
7 purchase totals =	$695.02		$730.2115	$730.22	$730.25	$730.10