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	$196.94	6.194%	$209.1385	$209.14	$209.15	$209.10
Purchase #2	$132.80	7.118%	$142.2527	$142.25	$142.25	$142.30
Purchase #3	$131.89	11.361%	$146.874	$146.87	$146.85	$146.90
Purchase #4	$149.59	3.773%	$155.234	$155.23	$155.25	$155.20
Purchase #5	$167.42	13.428%	$189.9012	$189.90	$189.90	$189.90
Purchase #6	$83.82	6.647%	$89.3915	$89.39	$89.40	$89.40
Purchase #7	$181.85	9.378%	$198.9039	$198.90	$198.90	$198.90
7 purchase totals =	$1,044.31		$1,131.6958	$1,131.68	$1,131.70	$1,131.70