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	$188.25	5.620%	$198.8297	$198.83	$198.85	$198.80
Purchase #2	$155.29	10.308%	$171.2973	$171.30	$171.30	$171.30
Purchase #3	$94.88	12.107%	$106.3671	$106.37	$106.35	$106.40
Purchase #4	$13.46	13.136%	$15.2281	$15.23	$15.25	$15.20
Purchase #5	$31.46	11.694%	$35.1389	$35.14	$35.15	$35.10
Purchase #6	$73.42	6.287%	$78.0359	$78.04	$78.05	$78.00
Purchase #7	$217.30	5.654%	$229.5861	$229.59	$229.60	$229.60
7 purchase totals =	$774.06		$834.4831	$834.50	$834.55	$834.40