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	$100.26	11.423%	$111.7127	$111.71	$111.70	$111.70
Purchase #2	$170.74	12.221%	$191.6061	$191.61	$191.60	$191.60
Purchase #3	$214.64	12.134%	$240.6844	$240.68	$240.70	$240.70
Purchase #4	$217.53	10.515%	$240.4033	$240.40	$240.40	$240.40
Purchase #5	$92.56	9.869%	$101.6947	$101.69	$101.70	$101.70
Purchase #6	$92.65	10.118%	$102.0243	$102.02	$102.00	$102.00
Purchase #7	$11.38	13.349%	$12.8991	$12.90	$12.90	$12.90
7 purchase totals =	$899.76		$1,001.0246	$1,001.01	$1,001.00	$1,001.00