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	$143.40	3.774%	$148.8119	$148.81	$148.80	$148.80
Purchase #2	$53.37	11.649%	$59.5871	$59.59	$59.60	$59.60
Purchase #3	$61.65	10.390%	$68.0554	$68.06	$68.05	$68.10
Purchase #4	$169.55	9.533%	$185.7132	$185.71	$185.70	$185.70
Purchase #5	$218.30	11.404%	$243.1949	$243.19	$243.20	$243.20
Purchase #6	$200.90	4.715%	$210.3724	$210.37	$210.35	$210.40
Purchase #7	$54.34	11.162%	$60.4054	$60.41	$60.40	$60.40
7 purchase totals =	$901.51		$976.1403	$976.14	$976.10	$976.20