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	$82.75	7.766%	$89.1764	$89.18	$89.20	$89.20
Purchase #2	$93.83	11.442%	$104.566	$104.57	$104.55	$104.60
Purchase #3	$184.96	9.155%	$201.8931	$201.89	$201.90	$201.90
Purchase #4	$149.76	4.177%	$156.0155	$156.02	$156.00	$156.00
Purchase #5	$180.97	10.673%	$200.2849	$200.28	$200.30	$200.30
Purchase #6	$192.63	13.723%	$219.0646	$219.06	$219.05	$219.10
Purchase #7	$59.90	9.213%	$65.4186	$65.42	$65.40	$65.40
7 purchase totals =	$944.80		$1,036.4191	$1,036.42	$1,036.40	$1,036.50