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	$185.96	12.785%	$209.735	$209.74	$209.75	$209.70
Purchase #2	$25.54	8.729%	$27.7694	$27.77	$27.75	$27.80
Purchase #3	$137.98	13.599%	$156.7439	$156.74	$156.75	$156.70
Purchase #4	$74.75	4.348%	$78.0001	$78.00	$78.00	$78.00
Purchase #5	$68.94	13.669%	$78.3634	$78.36	$78.35	$78.40
Purchase #6	$162.88	6.570%	$173.5812	$173.58	$173.60	$173.60
Purchase #7	$6.55	11.323%	$7.2917	$7.29	$7.30	$7.30
7 purchase totals =	$662.60		$731.4847	$731.48	$731.50	$731.50