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	$185.26	3.130%	$191.0586	$191.06	$191.05	$191.10
Purchase #2	$18.76	7.873%	$20.237	$20.24	$20.25	$20.20
Purchase #3	$18.53	13.694%	$21.0675	$21.07	$21.05	$21.10
Purchase #4	$81.34	6.636%	$86.7377	$86.74	$86.75	$86.70
Purchase #5	$149.32	12.788%	$168.415	$168.42	$168.40	$168.40
Purchase #6	$9.67	10.453%	$10.6808	$10.68	$10.70	$10.70
Purchase #7	$82.39	8.835%	$89.6692	$89.67	$89.65	$89.70
7 purchase totals =	$545.27		$587.8658	$587.88	$587.85	$587.90