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	$101.88	7.633%	$109.6565	$109.66	$109.65	$109.70
Purchase #2	$150.92	12.390%	$169.619	$169.62	$169.60	$169.60
Purchase #3	$163.28	3.545%	$169.0683	$169.07	$169.05	$169.10
Purchase #4	$166.49	11.453%	$185.5581	$185.56	$185.55	$185.60
Purchase #5	$59.44	3.329%	$61.4188	$61.42	$61.40	$61.40
Purchase #6	$120.38	3.754%	$124.8991	$124.90	$124.90	$124.90
Purchase #7	$197.99	10.408%	$218.5968	$218.60	$218.60	$218.60
7 purchase totals =	$960.38		$1,038.8166	$1,038.83	$1,038.75	$1,038.90