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	$96.32	13.682%	$109.4985	$109.50	$109.50	$109.50
Purchase #2	$191.88	11.264%	$213.4934	$213.49	$213.50	$213.50
Purchase #3	$85.86	5.487%	$90.5711	$90.57	$90.55	$90.60
Purchase #4	$214.71	13.510%	$243.7173	$243.72	$243.70	$243.70
Purchase #5	$181.27	7.829%	$195.4616	$195.46	$195.45	$195.50
Purchase #6	$85.74	12.723%	$96.6487	$96.65	$96.65	$96.60
Purchase #7	$10.33	12.125%	$11.5825	$11.58	$11.60	$11.60
7 purchase totals =	$866.11		$960.9731	$960.97	$960.95	$961.00