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	$169.89	13.690%	$193.1479	$193.15	$193.15	$193.10
Purchase #2	$178.88	9.762%	$196.3423	$196.34	$196.35	$196.30
Purchase #3	$220.49	13.544%	$250.3532	$250.35	$250.35	$250.40
Purchase #4	$131.83	5.147%	$138.6153	$138.62	$138.60	$138.60
Purchase #5	$184.54	5.218%	$194.1693	$194.17	$194.15	$194.20
Purchase #6	$37.64	7.781%	$40.5688	$40.57	$40.55	$40.60
Purchase #7	$229.91	11.285%	$255.8553	$255.86	$255.85	$255.90
7 purchase totals =	$1,153.18		$1,269.0521	$1,269.06	$1,269.00	$1,269.10