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	$159.32	4.503%	$166.4942	$166.49	$166.50	$166.50
Purchase #2	$62.50	8.603%	$67.8769	$67.88	$67.90	$67.90
Purchase #3	$93.95	5.587%	$99.199	$99.20	$99.20	$99.20
Purchase #4	$85.69	12.699%	$96.5718	$96.57	$96.55	$96.60
Purchase #5	$106.26	5.213%	$111.7993	$111.80	$111.80	$111.80
Purchase #6	$221.59	7.673%	$238.5926	$238.59	$238.60	$238.60
Purchase #7	$209.85	13.664%	$238.5239	$238.52	$238.50	$238.50
7 purchase totals =	$939.16		$1,019.0577	$1,019.05	$1,019.05	$1,019.10