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	$242.99	8.418%	$263.4449	$263.44	$263.45	$263.40
Purchase #2	$48.29	11.142%	$53.6705	$53.67	$53.65	$53.70
Purchase #3	$100.34	5.487%	$105.8457	$105.85	$105.85	$105.80
Purchase #4	$144.61	4.685%	$151.385	$151.39	$151.40	$151.40
Purchase #5	$59.95	6.273%	$63.7107	$63.71	$63.70	$63.70
Purchase #6	$56.32	8.507%	$61.1111	$61.11	$61.10	$61.10
Purchase #7	$156.92	7.426%	$168.5729	$168.57	$168.55	$168.60
7 purchase totals =	$809.42		$867.7408	$867.74	$867.70	$867.70