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	$7.46	3.154%	$7.6953	$7.70	$7.70	$7.70
Purchase #2	$102.90	5.736%	$108.8023	$108.80	$108.80	$108.80
Purchase #3	$52.91	5.571%	$55.8576	$55.86	$55.85	$55.90
Purchase #4	$222.91	12.371%	$250.4862	$250.49	$250.50	$250.50
Purchase #5	$157.88	8.269%	$170.9351	$170.94	$170.95	$170.90
Purchase #6	$213.60	4.809%	$223.872	$223.87	$223.85	$223.90
Purchase #7	$235.40	6.275%	$250.1714	$250.17	$250.15	$250.20
7 purchase totals =	$993.06		$1,067.8199	$1,067.83	$1,067.80	$1,067.90