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	$29.57	9.537%	$32.3901	$32.39	$32.40	$32.40
Purchase #2	$57.76	8.111%	$62.4449	$62.44	$62.45	$62.40
Purchase #3	$65.83	9.711%	$72.2228	$72.22	$72.20	$72.20
Purchase #4	$81.59	8.638%	$88.6377	$88.64	$88.65	$88.60
Purchase #5	$162.65	11.703%	$181.6849	$181.68	$181.70	$181.70
Purchase #6	$13.91	7.463%	$14.9481	$14.95	$14.95	$14.90
Purchase #7	$100.65	8.384%	$109.0885	$109.09	$109.10	$109.10
7 purchase totals =	$511.96		$561.4170	$561.41	$561.45	$561.30