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	$201.45	9.385%	$220.3561	$220.36	$220.35	$220.40
Purchase #2	$167.52	13.666%	$190.4133	$190.41	$190.40	$190.40
Purchase #3	$69.53	4.742%	$72.8271	$72.83	$72.85	$72.80
Purchase #4	$89.29	12.586%	$100.528	$100.53	$100.55	$100.50
Purchase #5	$131.82	4.231%	$137.3973	$137.40	$137.40	$137.40
Purchase #6	$65.87	11.703%	$73.5788	$73.58	$73.60	$73.60
Purchase #7	$240.34	6.654%	$256.3322	$256.33	$256.35	$256.30
7 purchase totals =	$965.82		$1,051.4328	$1,051.44	$1,051.50	$1,051.40