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	$177.57	7.858%	$191.5235	$191.52	$191.50	$191.50
Purchase #2	$136.55	10.707%	$151.1704	$151.17	$151.15	$151.20
Purchase #3	$189.68	11.159%	$210.8464	$210.85	$210.85	$210.80
Purchase #4	$17.32	8.458%	$18.7849	$18.78	$18.80	$18.80
Purchase #5	$198.99	12.323%	$223.5115	$223.51	$223.50	$223.50
Purchase #6	$109.36	8.568%	$118.73	$118.73	$118.75	$118.70
Purchase #7	$216.94	11.347%	$241.5562	$241.56	$241.55	$241.60
7 purchase totals =	$1,046.41		$1,156.1229	$1,156.12	$1,156.10	$1,156.10