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	$54.68	12.180%	$61.34	$61.34	$61.35	$61.30
Purchase #2	$78.73	6.146%	$83.5687	$83.57	$83.55	$83.60
Purchase #3	$196.62	11.181%	$218.6041	$218.60	$218.60	$218.60
Purchase #4	$165.95	10.783%	$183.8444	$183.84	$183.85	$183.80
Purchase #5	$166.34	10.283%	$183.4447	$183.44	$183.45	$183.40
Purchase #6	$17.92	8.844%	$19.5048	$19.50	$19.50	$19.50
Purchase #7	$198.77	12.550%	$223.7156	$223.72	$223.70	$223.70
7 purchase totals =	$879.01		$974.0223	$974.01	$974.00	$973.90