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	$241.73	10.696%	$267.5854	$267.59	$267.60	$267.60
Purchase #2	$194.28	10.518%	$214.7144	$214.71	$214.70	$214.70
Purchase #3	$69.62	3.253%	$71.8847	$71.88	$71.90	$71.90
Purchase #4	$42.45	13.828%	$48.32	$48.32	$48.30	$48.30
Purchase #5	$83.93	11.700%	$93.7498	$93.75	$93.75	$93.70
Purchase #6	$126.97	11.311%	$141.3316	$141.33	$141.35	$141.30
Purchase #7	$160.30	3.433%	$165.8031	$165.80	$165.80	$165.80
7 purchase totals =	$919.28		$1,003.3890	$1,003.38	$1,003.40	$1,003.30