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	$98.43	11.602%	$109.8498	$109.85	$109.85	$109.80
Purchase #2	$130.86	10.690%	$144.8489	$144.85	$144.85	$144.80
Purchase #3	$148.77	9.330%	$162.6502	$162.65	$162.65	$162.70
Purchase #4	$116.88	12.177%	$131.1125	$131.11	$131.10	$131.10
Purchase #5	$233.99	12.167%	$262.4596	$262.46	$262.45	$262.50
Purchase #6	$184.29	9.478%	$201.757	$201.76	$201.75	$201.80
Purchase #7	$128.66	3.794%	$133.5414	$133.54	$133.55	$133.50
7 purchase totals =	$1,041.88		$1,146.2194	$1,146.22	$1,146.20	$1,146.20