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	$201.76	9.660%	$221.25	$221.25	$221.25	$221.30
Purchase #2	$37.92	7.409%	$40.7295	$40.73	$40.75	$40.70
Purchase #3	$52.39	3.445%	$54.1948	$54.19	$54.20	$54.20
Purchase #4	$38.50	11.512%	$42.9321	$42.93	$42.95	$42.90
Purchase #5	$233.44	4.278%	$243.4266	$243.43	$243.45	$243.40
Purchase #6	$238.48	11.502%	$265.91	$265.91	$265.90	$265.90
Purchase #7	$121.56	4.800%	$127.3949	$127.39	$127.40	$127.40
7 purchase totals =	$924.05		$995.8379	$995.83	$995.90	$995.80