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	$233.67	4.356%	$243.8487	$243.85	$243.85	$243.80
Purchase #2	$90.71	7.407%	$97.4289	$97.43	$97.45	$97.40
Purchase #3	$117.54	10.355%	$129.7113	$129.71	$129.70	$129.70
Purchase #4	$240.65	5.805%	$254.6197	$254.62	$254.60	$254.60
Purchase #5	$74.31	10.207%	$81.8948	$81.89	$81.90	$81.90
Purchase #6	$20.28	6.468%	$21.5917	$21.59	$21.60	$21.60
Purchase #7	$245.51	4.608%	$256.8231	$256.82	$256.80	$256.80
7 purchase totals =	$1,022.67		$1,085.9182	$1,085.91	$1,085.90	$1,085.80