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	$233.32	13.440%	$264.6782	$264.68	$264.70	$264.70
Purchase #2	$242.75	6.518%	$258.5724	$258.57	$258.55	$258.60
Purchase #3	$56.62	5.864%	$59.9402	$59.94	$59.95	$59.90
Purchase #4	$83.67	12.471%	$94.1045	$94.10	$94.10	$94.10
Purchase #5	$29.50	13.525%	$33.4899	$33.49	$33.50	$33.50
Purchase #6	$140.28	4.117%	$146.0553	$146.06	$146.05	$146.10
Purchase #7	$96.43	11.604%	$107.6197	$107.62	$107.60	$107.60
7 purchase totals =	$882.57		$964.4602	$964.46	$964.45	$964.50