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	$226.73	11.725%	$253.3141	$253.31	$253.30	$253.30
Purchase #2	$246.52	13.469%	$279.7238	$279.72	$279.70	$279.70
Purchase #3	$58.76	7.118%	$62.9425	$62.94	$62.95	$62.90
Purchase #4	$150.85	7.391%	$161.9993	$162.00	$162.00	$162.00
Purchase #5	$131.51	11.575%	$146.7323	$146.73	$146.75	$146.70
Purchase #6	$204.53	3.396%	$211.4758	$211.48	$211.50	$211.50
Purchase #7	$165.82	11.807%	$185.3984	$185.40	$185.40	$185.40
7 purchase totals =	$1,184.72		$1,301.5862	$1,301.58	$1,301.60	$1,301.50