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	$82.72	10.558%	$91.4536	$91.45	$91.45	$91.50
Purchase #2	$96.43	4.624%	$100.8889	$100.89	$100.90	$100.90
Purchase #3	$198.65	10.700%	$219.9056	$219.91	$219.90	$219.90
Purchase #4	$78.53	10.722%	$86.95	$86.95	$86.95	$87.00
Purchase #5	$233.61	3.763%	$242.4007	$242.40	$242.40	$242.40
Purchase #6	$121.57	7.375%	$130.5358	$130.54	$130.55	$130.50
Purchase #7	$224.72	13.835%	$255.81	$255.81	$255.80	$255.80
7 purchase totals =	$1,036.23		$1,127.9446	$1,127.95	$1,127.95	$1,128.00