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	$104.90	5.610%	$110.7849	$110.78	$110.80	$110.80
Purchase #2	$64.75	6.619%	$69.0358	$69.04	$69.05	$69.00
Purchase #3	$105.48	3.646%	$109.3258	$109.33	$109.35	$109.30
Purchase #4	$174.62	3.433%	$180.6147	$180.61	$180.60	$180.60
Purchase #5	$105.43	4.230%	$109.8897	$109.89	$109.90	$109.90
Purchase #6	$161.87	11.146%	$179.912	$179.91	$179.90	$179.90
Purchase #7	$41.43	5.170%	$43.5719	$43.57	$43.55	$43.60
7 purchase totals =	$758.48		$803.1348	$803.13	$803.15	$803.10