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	$82.31	13.684%	$93.5733	$93.57	$93.55	$93.60
Purchase #2	$37.69	10.491%	$41.6441	$41.64	$41.65	$41.60
Purchase #3	$240.79	12.320%	$270.4553	$270.46	$270.45	$270.50
Purchase #4	$196.28	5.122%	$206.3335	$206.33	$206.35	$206.30
Purchase #5	$19.40	4.241%	$20.2228	$20.22	$20.20	$20.20
Purchase #6	$50.34	6.664%	$53.6947	$53.69	$53.70	$53.70
Purchase #7	$79.29	3.834%	$82.33	$82.33	$82.35	$82.30
7 purchase totals =	$706.10		$768.2537	$768.24	$768.25	$768.20