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	$124.98	4.533%	$130.6453	$130.65	$130.65	$130.60
Purchase #2	$109.58	12.637%	$123.4276	$123.43	$123.45	$123.40
Purchase #3	$54.76	4.150%	$57.0325	$57.03	$57.05	$57.00
Purchase #4	$45.90	10.637%	$50.7824	$50.78	$50.80	$50.80
Purchase #5	$148.56	7.299%	$159.4034	$159.40	$159.40	$159.40
Purchase #6	$103.94	7.280%	$111.5068	$111.51	$111.50	$111.50
Purchase #7	$148.31	9.230%	$161.999	$162.00	$162.00	$162.00
7 purchase totals =	$736.03		$794.7970	$794.80	$794.85	$794.70