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	$135.71	13.113%	$153.5057	$153.51	$153.50	$153.50
Purchase #2	$111.76	7.135%	$119.7341	$119.73	$119.75	$119.70
Purchase #3	$147.36	7.815%	$158.8762	$158.88	$158.90	$158.90
Purchase #4	$195.85	11.648%	$218.6626	$218.66	$218.65	$218.70
Purchase #5	$39.42	8.737%	$42.8641	$42.86	$42.85	$42.90
Purchase #6	$153.81	7.293%	$165.0274	$165.03	$165.05	$165.00
Purchase #7	$184.78	3.344%	$190.959	$190.96	$190.95	$191.00
7 purchase totals =	$968.69		$1,049.6291	$1,049.63	$1,049.65	$1,049.70