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	$159.83	10.614%	$176.7944	$176.79	$176.80	$176.80
Purchase #2	$92.43	9.616%	$101.3181	$101.32	$101.30	$101.30
Purchase #3	$127.56	13.571%	$144.8712	$144.87	$144.85	$144.90
Purchase #4	$210.69	9.694%	$231.1143	$231.11	$231.10	$231.10
Purchase #5	$143.32	8.148%	$154.9977	$155.00	$155.00	$155.00
Purchase #6	$100.76	11.706%	$112.555	$112.56	$112.55	$112.60
Purchase #7	$155.35	10.645%	$171.887	$171.89	$171.90	$171.90
7 purchase totals =	$989.94		$1,093.5377	$1,093.54	$1,093.50	$1,093.60