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	$43.40	5.743%	$45.8925	$45.89	$45.90	$45.90
Purchase #2	$77.74	6.614%	$82.8817	$82.88	$82.90	$82.90
Purchase #3	$142.74	4.356%	$148.9578	$148.96	$148.95	$149.00
Purchase #4	$42.39	12.665%	$47.7587	$47.76	$47.75	$47.80
Purchase #5	$10.92	8.783%	$11.8791	$11.88	$11.90	$11.90
Purchase #6	$209.36	7.658%	$225.3928	$225.39	$225.40	$225.40
Purchase #7	$227.76	7.291%	$244.366	$244.37	$244.35	$244.40
7 purchase totals =	$754.31		$807.1286	$807.13	$807.15	$807.30