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	$42.87	7.113%	$45.9193	$45.92	$45.90	$45.90
Purchase #2	$189.35	12.374%	$212.7802	$212.78	$212.80	$212.80
Purchase #3	$177.81	5.516%	$187.618	$187.62	$187.60	$187.60
Purchase #4	$64.84	4.270%	$67.6087	$67.61	$67.60	$67.60
Purchase #5	$242.48	12.766%	$273.435	$273.44	$273.45	$273.40
Purchase #6	$198.57	4.833%	$208.1669	$208.17	$208.15	$208.20
Purchase #7	$152.36	12.671%	$171.6655	$171.67	$171.65	$171.70
7 purchase totals =	$1,068.28		$1,167.1936	$1,167.21	$1,167.15	$1,167.20