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	$94.98	10.408%	$104.8655	$104.87	$104.85	$104.90
Purchase #2	$128.34	9.517%	$140.5541	$140.55	$140.55	$140.60
Purchase #3	$46.65	10.193%	$51.405	$51.41	$51.40	$51.40
Purchase #4	$212.77	13.499%	$241.4918	$241.49	$241.50	$241.50
Purchase #5	$156.61	5.373%	$165.0247	$165.02	$165.00	$165.00
Purchase #6	$190.76	11.446%	$212.5944	$212.59	$212.60	$212.60
Purchase #7	$79.62	12.831%	$89.836	$89.84	$89.85	$89.80
7 purchase totals =	$909.73		$1,005.7715	$1,005.77	$1,005.75	$1,005.80