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	$46.97	7.154%	$50.3302	$50.33	$50.35	$50.30
Purchase #2	$221.31	9.114%	$241.4802	$241.48	$241.50	$241.50
Purchase #3	$90.91	13.587%	$103.2619	$103.26	$103.25	$103.30
Purchase #4	$120.85	3.385%	$124.9408	$124.94	$124.95	$124.90
Purchase #5	$40.83	11.215%	$45.4091	$45.41	$45.40	$45.40
Purchase #6	$180.60	8.608%	$196.146	$196.15	$196.15	$196.10
Purchase #7	$14.56	13.826%	$16.5731	$16.57	$16.55	$16.60
7 purchase totals =	$716.03		$778.1413	$778.14	$778.15	$778.10