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	$211.25	5.283%	$222.4103	$222.41	$222.40	$222.40
Purchase #2	$51.33	7.409%	$55.133	$55.13	$55.15	$55.10
Purchase #3	$64.69	10.332%	$71.3738	$71.37	$71.35	$71.40
Purchase #4	$245.86	5.255%	$258.7799	$258.78	$258.80	$258.80
Purchase #5	$129.53	9.439%	$141.7563	$141.76	$141.75	$141.80
Purchase #6	$85.60	12.218%	$96.0586	$96.06	$96.05	$96.10
Purchase #7	$166.68	13.597%	$189.3435	$189.34	$189.35	$189.30
7 purchase totals =	$954.94		$1,034.8554	$1,034.85	$1,034.85	$1,034.90