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	$218.79	4.721%	$229.1191	$229.12	$229.10	$229.10
Purchase #2	$57.84	4.550%	$60.4717	$60.47	$60.45	$60.50
Purchase #3	$78.93	4.626%	$82.5813	$82.58	$82.60	$82.60
Purchase #4	$225.69	12.515%	$253.9351	$253.94	$253.95	$253.90
Purchase #5	$51.35	5.394%	$54.1198	$54.12	$54.10	$54.10
Purchase #6	$32.42	10.802%	$35.922	$35.92	$35.90	$35.90
Purchase #7	$25.33	13.263%	$28.6895	$28.69	$28.70	$28.70
7 purchase totals =	$690.35		$744.8385	$744.84	$744.80	$744.80