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	$50.59	3.627%	$52.4249	$52.42	$52.40	$52.40
Purchase #2	$10.36	4.399%	$10.8157	$10.82	$10.80	$10.80
Purchase #3	$164.26	12.680%	$185.0882	$185.09	$185.10	$185.10
Purchase #4	$78.38	10.300%	$86.4531	$86.45	$86.45	$86.50
Purchase #5	$140.54	11.129%	$156.1807	$156.18	$156.20	$156.20
Purchase #6	$240.52	10.149%	$264.9304	$264.93	$264.95	$264.90
Purchase #7	$65.28	13.336%	$73.9857	$73.99	$74.00	$74.00
7 purchase totals =	$749.93		$829.8787	$829.88	$829.90	$829.90