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	$171.97	9.602%	$188.4826	$188.48	$188.50	$188.50
Purchase #2	$72.41	12.546%	$81.4946	$81.49	$81.50	$81.50
Purchase #3	$29.37	6.529%	$31.2876	$31.29	$31.30	$31.30
Purchase #4	$66.82	9.543%	$73.1966	$73.20	$73.20	$73.20
Purchase #5	$214.94	8.546%	$233.3088	$233.31	$233.30	$233.30
Purchase #6	$157.57	7.609%	$169.5595	$169.56	$169.55	$169.60
Purchase #7	$240.43	6.432%	$255.8945	$255.89	$255.90	$255.90
7 purchase totals =	$953.51		$1,033.2242	$1,033.22	$1,033.25	$1,033.30