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	$79.69	7.322%	$85.5249	$85.52	$85.50	$85.50
Purchase #2	$57.98	5.664%	$61.264	$61.26	$61.25	$61.30
Purchase #3	$171.54	12.805%	$193.5057	$193.51	$193.50	$193.50
Purchase #4	$100.30	5.222%	$105.5377	$105.54	$105.55	$105.50
Purchase #5	$245.96	8.379%	$266.569	$266.57	$266.55	$266.60
Purchase #6	$221.42	9.574%	$242.6188	$242.62	$242.60	$242.60
Purchase #7	$170.85	11.681%	$190.807	$190.81	$190.80	$190.80
7 purchase totals =	$1,047.74		$1,145.8271	$1,145.83	$1,145.75	$1,145.80