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	$246.35	9.335%	$269.3468	$269.35	$269.35	$269.30
Purchase #2	$159.76	8.191%	$172.8459	$172.85	$172.85	$172.80
Purchase #3	$40.30	3.713%	$41.7963	$41.80	$41.80	$41.80
Purchase #4	$160.50	3.326%	$165.8382	$165.84	$165.85	$165.80
Purchase #5	$93.56	6.321%	$99.4739	$99.47	$99.45	$99.50
Purchase #6	$25.55	11.467%	$28.4798	$28.48	$28.50	$28.50
Purchase #7	$142.37	8.134%	$153.9504	$153.95	$153.95	$154.00
7 purchase totals =	$868.39		$931.7313	$931.74	$931.75	$931.70