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	$66.42	10.347%	$73.2925	$73.29	$73.30	$73.30
Purchase #2	$190.31	11.623%	$212.4297	$212.43	$212.45	$212.40
Purchase #3	$234.96	6.312%	$249.7907	$249.79	$249.80	$249.80
Purchase #4	$156.29	7.581%	$168.1383	$168.14	$168.15	$168.10
Purchase #5	$76.62	8.746%	$83.3212	$83.32	$83.30	$83.30
Purchase #6	$146.46	12.146%	$164.249	$164.25	$164.25	$164.20
Purchase #7	$135.33	12.221%	$151.8687	$151.87	$151.85	$151.90
7 purchase totals =	$1,006.39		$1,103.0901	$1,103.09	$1,103.10	$1,103.00