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	$136.36	10.471%	$150.6383	$150.64	$150.65	$150.60
Purchase #2	$28.37	7.160%	$30.4013	$30.40	$30.40	$30.40
Purchase #3	$167.31	3.271%	$172.7827	$172.78	$172.80	$172.80
Purchase #4	$137.65	9.626%	$150.9002	$150.90	$150.90	$150.90
Purchase #5	$137.69	7.759%	$148.3734	$148.37	$148.35	$148.40
Purchase #6	$145.51	11.741%	$162.5943	$162.59	$162.60	$162.60
Purchase #7	$192.76	11.316%	$214.5727	$214.57	$214.55	$214.60
7 purchase totals =	$945.65		$1,030.2629	$1,030.25	$1,030.25	$1,030.30