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	$50.38	8.456%	$54.6401	$54.64	$54.65	$54.60
Purchase #2	$20.32	11.821%	$22.722	$22.72	$22.70	$22.70
Purchase #3	$94.34	10.675%	$104.4108	$104.41	$104.40	$104.40
Purchase #4	$196.52	4.273%	$204.9173	$204.92	$204.90	$204.90
Purchase #5	$81.58	9.636%	$89.441	$89.44	$89.45	$89.40
Purchase #6	$29.57	13.531%	$33.5711	$33.57	$33.55	$33.60
Purchase #7	$32.79	9.144%	$35.7883	$35.79	$35.80	$35.80
7 purchase totals =	$505.50		$545.4906	$545.49	$545.45	$545.40