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	$57.50	7.292%	$61.6929	$61.69	$61.70	$61.70
Purchase #2	$75.82	9.399%	$82.9463	$82.95	$82.95	$82.90
Purchase #3	$229.30	4.195%	$238.9191	$238.92	$238.90	$238.90
Purchase #4	$101.51	10.164%	$111.8275	$111.83	$111.85	$111.80
Purchase #5	$208.73	10.610%	$230.8763	$230.88	$230.90	$230.90
Purchase #6	$129.76	7.652%	$139.6892	$139.69	$139.70	$139.70
Purchase #7	$187.49	12.171%	$210.3094	$210.31	$210.30	$210.30
7 purchase totals =	$990.11		$1,076.2607	$1,076.27	$1,076.30	$1,076.20