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	$229.45	9.343%	$250.8875	$250.89	$250.90	$250.90
Purchase #2	$49.82	7.166%	$53.3901	$53.39	$53.40	$53.40
Purchase #3	$19.47	13.137%	$22.0278	$22.03	$22.05	$22.00
Purchase #4	$63.52	10.355%	$70.0975	$70.10	$70.10	$70.10
Purchase #5	$176.98	11.188%	$196.7805	$196.78	$196.80	$196.80
Purchase #6	$247.68	8.368%	$268.4059	$268.41	$268.40	$268.40
Purchase #7	$134.49	7.216%	$144.1948	$144.19	$144.20	$144.20
7 purchase totals =	$921.41		$1,005.7841	$1,005.79	$1,005.85	$1,005.80