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	$187.76	11.475%	$209.3055	$209.31	$209.30	$209.30
Purchase #2	$188.46	6.799%	$201.2734	$201.27	$201.25	$201.30
Purchase #3	$29.58	13.170%	$33.4757	$33.48	$33.50	$33.50
Purchase #4	$144.27	12.381%	$162.1321	$162.13	$162.15	$162.10
Purchase #5	$60.58	8.359%	$65.6439	$65.64	$65.65	$65.60
Purchase #6	$92.25	12.643%	$103.9132	$103.91	$103.90	$103.90
Purchase #7	$91.81	10.834%	$101.7567	$101.76	$101.75	$101.80
7 purchase totals =	$794.71		$877.5005	$877.50	$877.50	$877.50