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	$115.50	13.124%	$130.6582	$130.66	$130.65	$130.70
Purchase #2	$134.63	12.542%	$151.5153	$151.52	$151.50	$151.50
Purchase #3	$78.98	11.816%	$88.3123	$88.31	$88.30	$88.30
Purchase #4	$57.28	3.664%	$59.3787	$59.38	$59.40	$59.40
Purchase #5	$169.97	12.354%	$190.9681	$190.97	$190.95	$191.00
Purchase #6	$90.37	13.498%	$102.5681	$102.57	$102.55	$102.60
Purchase #7	$35.85	13.573%	$40.7159	$40.72	$40.70	$40.70
7 purchase totals =	$682.58		$764.1166	$764.13	$764.05	$764.20