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	$228.56	12.201%	$256.4466	$256.45	$256.45	$256.40
Purchase #2	$224.83	12.639%	$253.2463	$253.25	$253.25	$253.20
Purchase #3	$204.38	7.453%	$219.6124	$219.61	$219.60	$219.60
Purchase #4	$153.44	11.500%	$171.0856	$171.09	$171.10	$171.10
Purchase #5	$86.27	3.424%	$89.2239	$89.22	$89.20	$89.20
Purchase #6	$236.35	3.729%	$245.1635	$245.16	$245.15	$245.20
Purchase #7	$168.48	12.542%	$189.6108	$189.61	$189.60	$189.60
7 purchase totals =	$1,302.31		$1,424.3891	$1,424.39	$1,424.35	$1,424.30