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	$154.92	8.360%	$167.8713	$167.87	$167.85	$167.90
Purchase #2	$118.84	3.759%	$123.3072	$123.31	$123.30	$123.30
Purchase #3	$211.59	6.593%	$225.5401	$225.54	$225.55	$225.50
Purchase #4	$222.63	7.138%	$238.5213	$238.52	$238.50	$238.50
Purchase #5	$221.56	10.439%	$244.6886	$244.69	$244.70	$244.70
Purchase #6	$174.97	8.685%	$190.1661	$190.17	$190.15	$190.20
Purchase #7	$215.55	10.635%	$238.4737	$238.47	$238.45	$238.50
7 purchase totals =	$1,320.06		$1,428.5683	$1,428.57	$1,428.50	$1,428.60