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	$143.39	9.308%	$156.7367	$156.74	$156.75	$156.70
Purchase #2	$140.37	6.419%	$149.3804	$149.38	$149.40	$149.40
Purchase #3	$209.42	6.283%	$222.5779	$222.58	$222.60	$222.60
Purchase #4	$99.43	6.525%	$105.9178	$105.92	$105.90	$105.90
Purchase #5	$62.72	13.281%	$71.0498	$71.05	$71.05	$71.00
Purchase #6	$72.84	6.604%	$77.6504	$77.65	$77.65	$77.70
Purchase #7	$213.77	11.370%	$238.0756	$238.08	$238.10	$238.10
7 purchase totals =	$941.94		$1,021.3886	$1,021.40	$1,021.45	$1,021.40