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	$204.67	3.602%	$212.0422	$212.04	$212.05	$212.00
Purchase #2	$17.83	5.552%	$18.8199	$18.82	$18.80	$18.80
Purchase #3	$172.40	11.180%	$191.6743	$191.67	$191.65	$191.70
Purchase #4	$177.94	7.512%	$191.3069	$191.31	$191.30	$191.30
Purchase #5	$76.25	9.506%	$83.4983	$83.50	$83.50	$83.50
Purchase #6	$168.46	7.343%	$180.83	$180.83	$180.85	$180.80
Purchase #7	$167.64	12.398%	$188.424	$188.42	$188.40	$188.40
7 purchase totals =	$985.19		$1,066.5956	$1,066.59	$1,066.55	$1,066.50