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	$196.98	4.792%	$206.4193	$206.42	$206.40	$206.40
Purchase #2	$243.41	4.523%	$254.4194	$254.42	$254.40	$254.40
Purchase #3	$87.71	10.477%	$96.8994	$96.90	$96.90	$96.90
Purchase #4	$242.71	3.128%	$250.302	$250.30	$250.30	$250.30
Purchase #5	$130.28	10.483%	$143.9373	$143.94	$143.95	$143.90
Purchase #6	$63.87	9.822%	$70.1433	$70.14	$70.15	$70.10
Purchase #7	$42.82	9.862%	$47.0429	$47.04	$47.05	$47.00
7 purchase totals =	$1,007.78		$1,069.1636	$1,069.16	$1,069.15	$1,069.00