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	$34.95	5.492%	$36.8695	$36.87	$36.85	$36.90
Purchase #2	$108.61	9.473%	$118.8986	$118.90	$118.90	$118.90
Purchase #3	$187.44	4.871%	$196.5702	$196.57	$196.55	$196.60
Purchase #4	$32.52	8.465%	$35.2728	$35.27	$35.25	$35.30
Purchase #5	$125.27	7.221%	$134.3157	$134.32	$134.30	$134.30
Purchase #6	$152.74	12.548%	$171.9058	$171.91	$171.90	$171.90
Purchase #7	$71.49	5.614%	$75.5034	$75.50	$75.50	$75.50
7 purchase totals =	$713.02		$769.3360	$769.34	$769.25	$769.40