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	$81.49	12.654%	$91.8017	$91.80	$91.80	$91.80
Purchase #2	$133.45	13.449%	$151.3977	$151.40	$151.40	$151.40
Purchase #3	$74.68	11.165%	$83.018	$83.02	$83.00	$83.00
Purchase #4	$172.83	10.300%	$190.6315	$190.63	$190.65	$190.60
Purchase #5	$245.53	4.647%	$256.9398	$256.94	$256.95	$256.90
Purchase #6	$196.71	11.311%	$218.9599	$218.96	$218.95	$219.00
Purchase #7	$119.27	7.407%	$128.1043	$128.10	$128.10	$128.10
7 purchase totals =	$1,023.96		$1,120.8529	$1,120.85	$1,120.85	$1,120.80