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	$165.52	13.365%	$187.6417	$187.64	$187.65	$187.60
Purchase #2	$19.26	12.118%	$21.5939	$21.59	$21.60	$21.60
Purchase #3	$7.61	12.814%	$8.5851	$8.59	$8.60	$8.60
Purchase #4	$74.89	9.714%	$82.1648	$82.16	$82.15	$82.20
Purchase #5	$134.51	10.404%	$148.5044	$148.50	$148.50	$148.50
Purchase #6	$86.78	11.416%	$96.6868	$96.69	$96.70	$96.70
Purchase #7	$202.74	9.307%	$221.609	$221.61	$221.60	$221.60
7 purchase totals =	$691.31		$766.7857	$766.78	$766.80	$766.80