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	$68.45	5.144%	$71.9711	$71.97	$71.95	$72.00
Purchase #2	$33.34	7.278%	$35.7665	$35.77	$35.75	$35.80
Purchase #3	$88.36	12.144%	$99.0904	$99.09	$99.10	$99.10
Purchase #4	$40.67	5.172%	$42.7735	$42.77	$42.75	$42.80
Purchase #5	$112.25	13.480%	$127.3813	$127.38	$127.40	$127.40
Purchase #6	$231.66	7.213%	$248.3696	$248.37	$248.35	$248.40
Purchase #7	$117.95	7.263%	$126.5167	$126.52	$126.50	$126.50
7 purchase totals =	$692.68		$751.8691	$751.87	$751.80	$752.00