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	$132.45	13.489%	$150.3162	$150.32	$150.30	$150.30
Purchase #2	$209.69	13.838%	$238.7069	$238.71	$238.70	$238.70
Purchase #3	$107.88	3.304%	$111.4444	$111.44	$111.45	$111.40
Purchase #4	$143.39	13.438%	$162.6587	$162.66	$162.65	$162.70
Purchase #5	$79.37	7.517%	$85.3362	$85.34	$85.35	$85.30
Purchase #6	$200.57	11.103%	$222.8393	$222.84	$222.85	$222.80
Purchase #7	$152.63	5.117%	$160.4401	$160.44	$160.45	$160.40
7 purchase totals =	$1,025.98		$1,131.7418	$1,131.75	$1,131.75	$1,131.60