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	$109.26	3.843%	$113.4589	$113.46	$113.45	$113.50
Purchase #2	$165.46	6.557%	$176.3092	$176.31	$176.30	$176.30
Purchase #3	$19.83	3.243%	$20.4731	$20.47	$20.45	$20.50
Purchase #4	$219.91	12.372%	$247.1173	$247.12	$247.10	$247.10
Purchase #5	$177.51	3.709%	$184.0938	$184.09	$184.10	$184.10
Purchase #6	$233.27	7.298%	$250.294	$250.29	$250.30	$250.30
Purchase #7	$59.79	11.340%	$66.5702	$66.57	$66.55	$66.60
7 purchase totals =	$985.03		$1,058.3165	$1,058.31	$1,058.25	$1,058.40