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	$90.97	4.830%	$95.3639	$95.36	$95.35	$95.40
Purchase #2	$78.69	5.641%	$83.1289	$83.13	$83.15	$83.10
Purchase #3	$19.78	13.816%	$22.5128	$22.51	$22.50	$22.50
Purchase #4	$100.83	12.577%	$113.5114	$113.51	$113.50	$113.50
Purchase #5	$134.57	9.406%	$147.2277	$147.23	$147.25	$147.20
Purchase #6	$162.96	13.160%	$184.4055	$184.41	$184.40	$184.40
Purchase #7	$71.79	11.646%	$80.1507	$80.15	$80.15	$80.20
7 purchase totals =	$659.59		$726.3009	$726.30	$726.30	$726.30