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	$86.91	10.650%	$96.1659	$96.17	$96.15	$96.20
Purchase #2	$135.75	10.850%	$150.4789	$150.48	$150.50	$150.50
Purchase #3	$150.77	9.140%	$164.5504	$164.55	$164.55	$164.60
Purchase #4	$159.27	4.870%	$167.0264	$167.03	$167.05	$167.00
Purchase #5	$70.71	8.659%	$76.8328	$76.83	$76.85	$76.80
Purchase #6	$127.30	9.510%	$139.4062	$139.41	$139.40	$139.40
Purchase #7	$199.46	10.804%	$221.0097	$221.01	$221.00	$221.00
7 purchase totals =	$930.17		$1,015.4703	$1,015.48	$1,015.50	$1,015.50