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	$118.64	8.606%	$128.8502	$128.85	$128.85	$128.90
Purchase #2	$65.31	3.531%	$67.6161	$67.62	$67.60	$67.60
Purchase #3	$95.88	11.385%	$106.7959	$106.80	$106.80	$106.80
Purchase #4	$184.63	11.385%	$205.6501	$205.65	$205.65	$205.70
Purchase #5	$147.43	11.636%	$164.585	$164.59	$164.60	$164.60
Purchase #6	$143.31	10.642%	$158.5611	$158.56	$158.55	$158.60
Purchase #7	$154.96	12.541%	$174.3935	$174.39	$174.40	$174.40
7 purchase totals =	$910.16		$1,006.4519	$1,006.46	$1,006.45	$1,006.60