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	$201.34	10.564%	$222.6096	$222.61	$222.60	$222.60
Purchase #2	$101.90	10.150%	$112.2429	$112.24	$112.25	$112.20
Purchase #3	$167.67	6.310%	$178.25	$178.25	$178.25	$178.30
Purchase #4	$185.29	6.374%	$197.1004	$197.10	$197.10	$197.10
Purchase #5	$236.43	8.317%	$256.0939	$256.09	$256.10	$256.10
Purchase #6	$13.51	12.757%	$15.2335	$15.23	$15.25	$15.20
Purchase #7	$20.58	8.206%	$22.2688	$22.27	$22.25	$22.30
7 purchase totals =	$926.72		$1,003.7991	$1,003.79	$1,003.80	$1,003.80