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	$32.56	13.788%	$37.0494	$37.05	$37.05	$37.00
Purchase #2	$191.45	9.590%	$209.8101	$209.81	$209.80	$209.80
Purchase #3	$248.48	6.264%	$264.0448	$264.04	$264.05	$264.00
Purchase #4	$86.31	6.773%	$92.1558	$92.16	$92.15	$92.20
Purchase #5	$164.30	12.496%	$184.8309	$184.83	$184.85	$184.80
Purchase #6	$79.56	12.761%	$89.7127	$89.71	$89.70	$89.70
Purchase #7	$238.95	12.339%	$268.434	$268.43	$268.45	$268.40
7 purchase totals =	$1,041.61		$1,146.0377	$1,146.03	$1,146.05	$1,145.90