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	$201.55	13.740%	$229.243	$229.24	$229.25	$229.20
Purchase #2	$98.50	6.839%	$105.2364	$105.24	$105.25	$105.20
Purchase #3	$244.68	11.152%	$271.9667	$271.97	$271.95	$272.00
Purchase #4	$223.69	4.360%	$233.4429	$233.44	$233.45	$233.40
Purchase #5	$13.26	8.849%	$14.4334	$14.43	$14.45	$14.40
Purchase #6	$240.64	5.349%	$253.5118	$253.51	$253.50	$253.50
Purchase #7	$14.29	11.546%	$15.9399	$15.94	$15.95	$15.90
7 purchase totals =	$1,036.61		$1,123.7741	$1,123.77	$1,123.80	$1,123.60