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	$100.71	4.254%	$104.9942	$104.99	$105.00	$105.00
Purchase #2	$224.76	8.757%	$244.4422	$244.44	$244.45	$244.40
Purchase #3	$129.67	12.797%	$146.2639	$146.26	$146.25	$146.30
Purchase #4	$158.66	3.579%	$164.3384	$164.34	$164.35	$164.30
Purchase #5	$228.77	9.395%	$250.2629	$250.26	$250.25	$250.30
Purchase #6	$30.67	12.802%	$34.5964	$34.60	$34.60	$34.60
Purchase #7	$65.83	8.867%	$71.6671	$71.67	$71.65	$71.70
7 purchase totals =	$939.07		$1,016.5651	$1,016.56	$1,016.55	$1,016.60