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	$59.78	12.425%	$67.2077	$67.21	$67.20	$67.20
Purchase #2	$218.31	13.280%	$247.3016	$247.30	$247.30	$247.30
Purchase #3	$233.59	5.861%	$247.2807	$247.28	$247.30	$247.30
Purchase #4	$176.48	3.263%	$182.2385	$182.24	$182.25	$182.20
Purchase #5	$39.52	10.221%	$43.5593	$43.56	$43.55	$43.60
Purchase #6	$97.81	11.778%	$109.3301	$109.33	$109.35	$109.30
Purchase #7	$135.87	8.541%	$147.4747	$147.47	$147.45	$147.50
7 purchase totals =	$961.36		$1,044.3926	$1,044.39	$1,044.40	$1,044.40