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	$151.92	5.548%	$160.3485	$160.35	$160.35	$160.30
Purchase #2	$35.36	8.578%	$38.3932	$38.39	$38.40	$38.40
Purchase #3	$218.80	6.362%	$232.7201	$232.72	$232.70	$232.70
Purchase #4	$64.69	10.350%	$71.3854	$71.39	$71.40	$71.40
Purchase #5	$182.35	7.748%	$196.4785	$196.48	$196.50	$196.50
Purchase #6	$60.67	11.440%	$67.6106	$67.61	$67.60	$67.60
Purchase #7	$168.94	5.540%	$178.2993	$178.30	$178.30	$178.30
7 purchase totals =	$882.73		$945.2356	$945.24	$945.25	$945.20