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	$54.31	5.824%	$57.473	$57.47	$57.45	$57.50
Purchase #2	$75.73	4.237%	$78.9387	$78.94	$78.95	$78.90
Purchase #3	$127.43	5.119%	$133.9531	$133.95	$133.95	$134.00
Purchase #4	$9.66	3.807%	$10.0278	$10.03	$10.05	$10.00
Purchase #5	$64.89	10.774%	$71.8812	$71.88	$71.90	$71.90
Purchase #6	$68.52	5.722%	$72.4407	$72.44	$72.45	$72.40
Purchase #7	$69.66	11.504%	$77.6737	$77.67	$77.65	$77.70
7 purchase totals =	$470.20		$502.3882	$502.38	$502.40	$502.40