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	$141.93	7.312%	$152.3079	$152.31	$152.30	$152.30
Purchase #2	$186.79	6.603%	$199.1237	$199.12	$199.10	$199.10
Purchase #3	$153.96	8.406%	$166.9019	$166.90	$166.90	$166.90
Purchase #4	$177.57	4.856%	$186.1928	$186.19	$186.20	$186.20
Purchase #5	$142.98	6.857%	$152.7841	$152.78	$152.80	$152.80
Purchase #6	$218.52	10.168%	$240.7391	$240.74	$240.75	$240.70
Purchase #7	$48.82	10.316%	$53.8563	$53.86	$53.85	$53.90
7 purchase totals =	$1,070.57		$1,151.9058	$1,151.90	$1,151.90	$1,151.90