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	$143.88	6.245%	$152.8653	$152.87	$152.85	$152.90
Purchase #2	$189.77	11.193%	$211.011	$211.01	$211.00	$211.00
Purchase #3	$75.87	9.402%	$83.0033	$83.00	$83.00	$83.00
Purchase #4	$50.86	6.192%	$54.0093	$54.01	$54.00	$54.00
Purchase #5	$89.29	3.356%	$92.2866	$92.29	$92.30	$92.30
Purchase #6	$93.83	9.534%	$102.7758	$102.78	$102.80	$102.80
Purchase #7	$229.69	9.672%	$251.9056	$251.91	$251.90	$251.90
7 purchase totals =	$873.19		$947.8569	$947.87	$947.85	$947.90