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	$14.38	9.251%	$15.7103	$15.71	$15.70	$15.70
Purchase #2	$73.38	7.477%	$78.8666	$78.87	$78.85	$78.90
Purchase #3	$23.95	7.662%	$25.785	$25.79	$25.80	$25.80
Purchase #4	$233.69	9.148%	$255.068	$255.07	$255.05	$255.10
Purchase #5	$168.88	10.637%	$186.8438	$186.84	$186.85	$186.80
Purchase #6	$77.99	9.681%	$85.5402	$85.54	$85.55	$85.50
Purchase #7	$80.58	12.129%	$90.3535	$90.35	$90.35	$90.40
7 purchase totals =	$672.85		$738.1674	$738.17	$738.15	$738.20