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	$141.35	11.415%	$157.4851	$157.49	$157.50	$157.50
Purchase #2	$127.56	11.271%	$141.9373	$141.94	$141.95	$141.90
Purchase #3	$227.81	3.119%	$234.9154	$234.92	$234.90	$234.90
Purchase #4	$221.91	11.770%	$248.0288	$248.03	$248.05	$248.00
Purchase #5	$126.95	3.553%	$131.4605	$131.46	$131.45	$131.50
Purchase #6	$78.40	5.243%	$82.5105	$82.51	$82.50	$82.50
Purchase #7	$106.48	3.577%	$110.2888	$110.29	$110.30	$110.30
7 purchase totals =	$1,030.46		$1,106.6264	$1,106.64	$1,106.65	$1,106.60