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	$35.96	3.271%	$37.1363	$37.14	$37.15	$37.10
Purchase #2	$18.39	11.823%	$20.5642	$20.56	$20.55	$20.60
Purchase #3	$43.25	9.591%	$47.3981	$47.40	$47.40	$47.40
Purchase #4	$98.97	5.338%	$104.253	$104.25	$104.25	$104.30
Purchase #5	$38.97	6.483%	$41.4964	$41.50	$41.50	$41.50
Purchase #6	$34.64	9.598%	$37.9647	$37.96	$37.95	$38.00
Purchase #7	$31.49	5.495%	$33.2204	$33.22	$33.20	$33.20
7 purchase totals =	$301.67		$322.0331	$322.03	$322.00	$322.10