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	$185.28	3.702%	$192.1391	$192.14	$192.15	$192.10
Purchase #2	$78.55	9.703%	$86.1717	$86.17	$86.15	$86.20
Purchase #3	$35.42	4.796%	$37.1187	$37.12	$37.10	$37.10
Purchase #4	$247.44	7.810%	$266.7651	$266.77	$266.75	$266.80
Purchase #5	$206.90	12.802%	$233.3873	$233.39	$233.40	$233.40
Purchase #6	$185.85	5.710%	$196.462	$196.46	$196.45	$196.50
Purchase #7	$130.88	5.431%	$137.9881	$137.99	$138.00	$138.00
7 purchase totals =	$1,070.32		$1,150.0320	$1,150.04	$1,150.00	$1,150.10