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	$127.41	3.405%	$131.7483	$131.75	$131.75	$131.70
Purchase #2	$249.63	4.784%	$261.5723	$261.57	$261.55	$261.60
Purchase #3	$102.37	6.795%	$109.326	$109.33	$109.35	$109.30
Purchase #4	$60.48	11.408%	$67.3796	$67.38	$67.40	$67.40
Purchase #5	$98.42	7.595%	$105.895	$105.90	$105.90	$105.90
Purchase #6	$22.56	13.827%	$25.6794	$25.68	$25.70	$25.70
Purchase #7	$224.78	10.335%	$248.011	$248.01	$248.00	$248.00
7 purchase totals =	$885.65		$949.6116	$949.62	$949.65	$949.60