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	$146.63	10.749%	$162.3913	$162.39	$162.40	$162.40
Purchase #2	$50.75	3.475%	$52.5136	$52.51	$52.50	$52.50
Purchase #3	$140.57	7.118%	$150.5758	$150.58	$150.60	$150.60
Purchase #4	$133.86	12.482%	$150.5684	$150.57	$150.55	$150.60
Purchase #5	$76.33	8.463%	$82.7898	$82.79	$82.80	$82.80
Purchase #6	$115.31	10.796%	$127.7589	$127.76	$127.75	$127.80
Purchase #7	$43.79	11.797%	$48.9559	$48.96	$48.95	$49.00
7 purchase totals =	$707.24		$775.5537	$775.56	$775.55	$775.70