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	$141.37	4.439%	$147.6454	$147.65	$147.65	$147.60
Purchase #2	$49.57	7.126%	$53.1024	$53.10	$53.10	$53.10
Purchase #3	$246.93	10.204%	$272.1267	$272.13	$272.15	$272.10
Purchase #4	$152.59	7.530%	$164.08	$164.08	$164.10	$164.10
Purchase #5	$227.97	11.176%	$253.4479	$253.45	$253.45	$253.40
Purchase #6	$107.74	11.668%	$120.3111	$120.31	$120.30	$120.30
Purchase #7	$77.49	6.181%	$82.2797	$82.28	$82.30	$82.30
7 purchase totals =	$1,003.66		$1,092.9932	$1,093.00	$1,093.05	$1,092.90