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	$29.48	13.166%	$33.3613	$33.36	$33.35	$33.40
Purchase #2	$137.59	7.124%	$147.3919	$147.39	$147.40	$147.40
Purchase #3	$111.33	6.821%	$118.9238	$118.92	$118.90	$118.90
Purchase #4	$55.70	7.268%	$59.7483	$59.75	$59.75	$59.70
Purchase #5	$195.45	13.724%	$222.2736	$222.27	$222.25	$222.30
Purchase #6	$249.33	4.789%	$261.2704	$261.27	$261.25	$261.30
Purchase #7	$40.56	4.377%	$42.3353	$42.34	$42.35	$42.30
7 purchase totals =	$819.44		$885.3046	$885.30	$885.25	$885.30