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	$99.94	12.396%	$112.3286	$112.33	$112.35	$112.30
Purchase #2	$199.37	13.280%	$225.8463	$225.85	$225.85	$225.80
Purchase #3	$159.95	8.142%	$172.9731	$172.97	$172.95	$173.00
Purchase #4	$214.77	9.291%	$234.7243	$234.72	$234.70	$234.70
Purchase #5	$218.35	12.188%	$244.9625	$244.96	$244.95	$245.00
Purchase #6	$58.61	4.745%	$61.391	$61.39	$61.40	$61.40
Purchase #7	$162.83	11.355%	$181.3193	$181.32	$181.30	$181.30
7 purchase totals =	$1,113.82		$1,233.5451	$1,233.54	$1,233.50	$1,233.50