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	$221.93	6.113%	$235.4966	$235.50	$235.50	$235.50
Purchase #2	$33.48	5.257%	$35.24	$35.24	$35.25	$35.20
Purchase #3	$59.73	12.773%	$67.3593	$67.36	$67.35	$67.40
Purchase #4	$90.37	12.102%	$101.3066	$101.31	$101.30	$101.30
Purchase #5	$50.47	11.797%	$56.4239	$56.42	$56.40	$56.40
Purchase #6	$151.89	12.598%	$171.0251	$171.03	$171.05	$171.00
Purchase #7	$17.84	4.232%	$18.595	$18.60	$18.60	$18.60
7 purchase totals =	$625.71		$685.4465	$685.46	$685.45	$685.40