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	$127.61	13.439%	$144.7595	$144.76	$144.75	$144.80
Purchase #2	$169.95	11.257%	$189.0813	$189.08	$189.10	$189.10
Purchase #3	$187.71	3.482%	$194.2461	$194.25	$194.25	$194.20
Purchase #4	$156.96	5.384%	$165.4107	$165.41	$165.40	$165.40
Purchase #5	$239.90	4.666%	$251.0937	$251.09	$251.10	$251.10
Purchase #6	$231.44	3.709%	$240.0241	$240.02	$240.00	$240.00
Purchase #7	$158.32	3.763%	$164.2776	$164.28	$164.30	$164.30
7 purchase totals =	$1,271.89		$1,348.8930	$1,348.89	$1,348.90	$1,348.90