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	$135.39	12.188%	$151.8913	$151.89	$151.90	$151.90
Purchase #2	$147.52	10.370%	$162.8178	$162.82	$162.80	$162.80
Purchase #3	$203.26	7.610%	$218.7281	$218.73	$218.75	$218.70
Purchase #4	$104.49	11.229%	$116.2232	$116.22	$116.20	$116.20
Purchase #5	$140.63	12.634%	$158.3972	$158.40	$158.40	$158.40
Purchase #6	$53.77	7.112%	$57.5941	$57.59	$57.60	$57.60
Purchase #7	$187.80	6.134%	$199.3197	$199.32	$199.30	$199.30
7 purchase totals =	$972.86		$1,064.9714	$1,064.97	$1,064.95	$1,064.90