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	$197.89	12.392%	$222.4125	$222.41	$222.40	$222.40
Purchase #2	$29.73	9.744%	$32.6269	$32.63	$32.65	$32.60
Purchase #3	$219.45	4.221%	$228.713	$228.71	$228.70	$228.70
Purchase #4	$53.85	13.337%	$61.032	$61.03	$61.05	$61.00
Purchase #5	$157.44	10.749%	$174.3632	$174.36	$174.35	$174.40
Purchase #6	$161.45	4.546%	$168.7895	$168.79	$168.80	$168.80
Purchase #7	$172.54	5.761%	$182.48	$182.48	$182.50	$182.50
7 purchase totals =	$992.35		$1,070.4171	$1,070.41	$1,070.45	$1,070.40