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	$230.28	11.200%	$256.0714	$256.07	$256.05	$256.10
Purchase #2	$231.67	8.180%	$250.6206	$250.62	$250.60	$250.60
Purchase #3	$98.38	3.458%	$101.782	$101.78	$101.80	$101.80
Purchase #4	$184.66	3.265%	$190.6891	$190.69	$190.70	$190.70
Purchase #5	$231.88	5.404%	$244.4108	$244.41	$244.40	$244.40
Purchase #6	$161.78	3.523%	$167.4795	$167.48	$167.50	$167.50
Purchase #7	$89.75	10.376%	$99.0625	$99.06	$99.05	$99.10
7 purchase totals =	$1,228.40		$1,310.1159	$1,310.11	$1,310.10	$1,310.20