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	$186.56	5.176%	$196.2163	$196.22	$196.20	$196.20
Purchase #2	$73.81	3.111%	$76.1062	$76.11	$76.10	$76.10
Purchase #3	$243.37	8.170%	$263.2533	$263.25	$263.25	$263.30
Purchase #4	$108.64	13.720%	$123.5454	$123.55	$123.55	$123.50
Purchase #5	$46.46	3.420%	$48.0489	$48.05	$48.05	$48.00
Purchase #6	$57.42	13.379%	$65.1022	$65.10	$65.10	$65.10
Purchase #7	$37.63	8.185%	$40.71	$40.71	$40.70	$40.70
7 purchase totals =	$753.89		$812.9823	$812.99	$812.95	$812.90