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	$181.92	6.680%	$194.0723	$194.07	$194.05	$194.10
Purchase #2	$123.89	10.612%	$137.0372	$137.04	$137.05	$137.00
Purchase #3	$243.62	12.134%	$273.1809	$273.18	$273.20	$273.20
Purchase #4	$235.75	3.520%	$244.0484	$244.05	$244.05	$244.00
Purchase #5	$165.28	5.564%	$174.4762	$174.48	$174.50	$174.50
Purchase #6	$40.43	12.102%	$45.3228	$45.32	$45.30	$45.30
Purchase #7	$30.83	13.553%	$35.0084	$35.01	$35.00	$35.00
7 purchase totals =	$1,021.72		$1,103.1462	$1,103.15	$1,103.15	$1,103.10