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	$226.41	4.413%	$236.4015	$236.40	$236.40	$236.40
Purchase #2	$6.65	13.325%	$7.5361	$7.54	$7.55	$7.50
Purchase #3	$145.72	11.428%	$162.3729	$162.37	$162.35	$162.40
Purchase #4	$14.25	11.737%	$15.9225	$15.92	$15.90	$15.90
Purchase #5	$18.94	13.398%	$21.4776	$21.48	$21.50	$21.50
Purchase #6	$196.65	9.323%	$214.9837	$214.98	$215.00	$215.00
Purchase #7	$99.51	6.223%	$105.7025	$105.70	$105.70	$105.70
7 purchase totals =	$708.13		$764.3968	$764.39	$764.40	$764.40