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	$89.35	11.192%	$99.3501	$99.35	$99.35	$99.40
Purchase #2	$37.42	10.237%	$41.2507	$41.25	$41.25	$41.30
Purchase #3	$75.45	4.479%	$78.8294	$78.83	$78.85	$78.80
Purchase #4	$173.95	10.424%	$192.0825	$192.08	$192.10	$192.10
Purchase #5	$61.99	12.137%	$69.5137	$69.51	$69.50	$69.50
Purchase #6	$141.56	13.596%	$160.8065	$160.81	$160.80	$160.80
Purchase #7	$196.39	7.405%	$210.9327	$210.93	$210.95	$210.90
7 purchase totals =	$776.11		$852.7656	$852.76	$852.80	$852.80