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	$209.91	11.224%	$233.4703	$233.47	$233.45	$233.50
Purchase #2	$104.51	13.873%	$119.0087	$119.01	$119.00	$119.00
Purchase #3	$174.80	12.155%	$196.0469	$196.05	$196.05	$196.00
Purchase #4	$231.40	7.806%	$249.4631	$249.46	$249.45	$249.50
Purchase #5	$28.26	4.318%	$29.4803	$29.48	$29.50	$29.50
Purchase #6	$140.87	4.648%	$147.4176	$147.42	$147.40	$147.40
Purchase #7	$88.90	10.297%	$98.054	$98.05	$98.05	$98.10
7 purchase totals =	$978.65		$1,072.9409	$1,072.94	$1,072.90	$1,073.00