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	$171.71	11.309%	$191.1287	$191.13	$191.15	$191.10
Purchase #2	$156.67	7.694%	$168.7242	$168.72	$168.70	$168.70
Purchase #3	$154.94	3.376%	$160.1708	$160.17	$160.15	$160.20
Purchase #4	$133.75	5.806%	$141.5155	$141.52	$141.50	$141.50
Purchase #5	$198.28	7.143%	$212.4431	$212.44	$212.45	$212.40
Purchase #6	$141.86	7.384%	$152.3349	$152.33	$152.35	$152.30
Purchase #7	$131.51	8.242%	$142.3491	$142.35	$142.35	$142.30
7 purchase totals =	$1,088.72		$1,168.6663	$1,168.66	$1,168.65	$1,168.50