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	$52.54	11.245%	$58.4481	$58.45	$58.45	$58.40
Purchase #2	$130.55	5.430%	$137.6389	$137.64	$137.65	$137.60
Purchase #3	$54.59	13.358%	$61.8821	$61.88	$61.90	$61.90
Purchase #4	$195.38	7.564%	$210.1585	$210.16	$210.15	$210.20
Purchase #5	$224.39	7.829%	$241.9575	$241.96	$241.95	$242.00
Purchase #6	$219.28	13.727%	$249.3806	$249.38	$249.40	$249.40
Purchase #7	$153.86	9.442%	$168.3875	$168.39	$168.40	$168.40
7 purchase totals =	$1,030.59		$1,127.8532	$1,127.86	$1,127.90	$1,127.90