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	$54.96	12.200%	$61.6651	$61.67	$61.65	$61.70
Purchase #2	$202.54	6.650%	$216.0089	$216.01	$216.00	$216.00
Purchase #3	$139.37	4.354%	$145.4382	$145.44	$145.45	$145.40
Purchase #4	$108.76	10.237%	$119.8938	$119.89	$119.90	$119.90
Purchase #5	$73.70	8.323%	$79.8341	$79.83	$79.85	$79.80
Purchase #6	$84.83	5.768%	$89.723	$89.72	$89.70	$89.70
Purchase #7	$211.32	10.193%	$232.8598	$232.86	$232.85	$232.90
7 purchase totals =	$875.48		$945.4229	$945.42	$945.40	$945.40