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	$45.87	5.367%	$48.3318	$48.33	$48.35	$48.30
Purchase #2	$231.31	10.597%	$255.8219	$255.82	$255.80	$255.80
Purchase #3	$100.71	10.143%	$110.925	$110.93	$110.95	$110.90
Purchase #4	$175.61	9.234%	$191.8258	$191.83	$191.85	$191.80
Purchase #5	$135.26	9.366%	$147.9285	$147.93	$147.95	$147.90
Purchase #6	$147.77	13.124%	$167.1633	$167.16	$167.15	$167.20
Purchase #7	$128.69	4.798%	$134.8645	$134.86	$134.85	$134.90
7 purchase totals =	$965.22		$1,056.8608	$1,056.86	$1,056.90	$1,056.80