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	$188.88	10.803%	$209.2847	$209.28	$209.30	$209.30
Purchase #2	$202.50	13.235%	$229.3009	$229.30	$229.30	$229.30
Purchase #3	$35.37	4.142%	$36.835	$36.84	$36.85	$36.80
Purchase #4	$41.68	4.697%	$43.6377	$43.64	$43.65	$43.60
Purchase #5	$166.59	9.466%	$182.3594	$182.36	$182.35	$182.40
Purchase #6	$208.28	5.540%	$219.8187	$219.82	$219.80	$219.80
Purchase #7	$74.29	10.696%	$82.2361	$82.24	$82.25	$82.20
7 purchase totals =	$917.59		$1,003.4725	$1,003.48	$1,003.50	$1,003.40