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	$69.76	4.223%	$72.706	$72.71	$72.70	$72.70
Purchase #2	$203.80	3.113%	$210.1443	$210.14	$210.15	$210.10
Purchase #3	$66.61	3.243%	$68.7702	$68.77	$68.75	$68.80
Purchase #4	$142.83	3.844%	$148.3204	$148.32	$148.30	$148.30
Purchase #5	$72.44	8.213%	$78.3895	$78.39	$78.40	$78.40
Purchase #6	$46.50	7.271%	$49.881	$49.88	$49.90	$49.90
Purchase #7	$59.75	12.365%	$67.1381	$67.14	$67.15	$67.10
7 purchase totals =	$661.69		$695.3495	$695.35	$695.35	$695.30