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	$95.47	8.761%	$103.8341	$103.83	$103.85	$103.80
Purchase #2	$13.52	12.388%	$15.1949	$15.19	$15.20	$15.20
Purchase #3	$114.51	11.454%	$127.626	$127.63	$127.65	$127.60
Purchase #4	$112.76	13.560%	$128.0503	$128.05	$128.05	$128.10
Purchase #5	$181.48	8.720%	$197.3051	$197.31	$197.30	$197.30
Purchase #6	$40.88	12.593%	$46.028	$46.03	$46.05	$46.00
Purchase #7	$96.53	9.663%	$105.8577	$105.86	$105.85	$105.90
7 purchase totals =	$655.15		$723.8961	$723.90	$723.95	$723.90