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	$85.54	6.850%	$91.3995	$91.40	$91.40	$91.40
Purchase #2	$67.26	13.532%	$76.3616	$76.36	$76.35	$76.40
Purchase #3	$90.34	9.661%	$99.0677	$99.07	$99.05	$99.10
Purchase #4	$228.89	11.385%	$254.9491	$254.95	$254.95	$254.90
Purchase #5	$102.91	11.134%	$114.368	$114.37	$114.35	$114.40
Purchase #6	$194.84	13.709%	$221.5506	$221.55	$221.55	$221.60
Purchase #7	$35.93	11.596%	$40.0964	$40.10	$40.10	$40.10
7 purchase totals =	$805.71		$897.7929	$897.80	$897.75	$897.90