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	$41.49	4.795%	$43.4794	$43.48	$43.50	$43.50
Purchase #2	$145.59	11.500%	$162.3329	$162.33	$162.35	$162.30
Purchase #3	$152.47	7.616%	$164.0821	$164.08	$164.10	$164.10
Purchase #4	$27.84	9.643%	$30.5246	$30.52	$30.50	$30.50
Purchase #5	$229.88	5.167%	$241.7579	$241.76	$241.75	$241.80
Purchase #6	$129.44	11.294%	$144.059	$144.06	$144.05	$144.10
Purchase #7	$145.74	13.441%	$165.3289	$165.33	$165.35	$165.30
7 purchase totals =	$872.45		$951.5648	$951.56	$951.60	$951.60