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	$153.85	4.424%	$160.6563	$160.66	$160.65	$160.70
Purchase #2	$20.87	3.137%	$21.5247	$21.52	$21.50	$21.50
Purchase #3	$89.77	11.571%	$100.1573	$100.16	$100.15	$100.20
Purchase #4	$133.41	7.424%	$143.3144	$143.31	$143.30	$143.30
Purchase #5	$233.38	13.555%	$265.0147	$265.01	$265.00	$265.00
Purchase #6	$179.30	5.536%	$189.226	$189.23	$189.25	$189.20
Purchase #7	$47.52	6.743%	$50.7243	$50.72	$50.70	$50.70
7 purchase totals =	$858.10		$930.6177	$930.61	$930.55	$930.60