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	$66.33	4.420%	$69.2618	$69.26	$69.25	$69.30
Purchase #2	$172.96	13.502%	$196.3131	$196.31	$196.30	$196.30
Purchase #3	$84.62	7.116%	$90.6416	$90.64	$90.65	$90.60
Purchase #4	$238.72	7.673%	$257.037	$257.04	$257.05	$257.00
Purchase #5	$235.42	10.814%	$260.8783	$260.88	$260.90	$260.90
Purchase #6	$90.87	13.359%	$103.0093	$103.01	$103.00	$103.00
Purchase #7	$176.29	11.655%	$196.8366	$196.84	$196.85	$196.80
7 purchase totals =	$1,065.21		$1,173.9777	$1,173.98	$1,174.00	$1,173.90