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	$193.73	6.762%	$206.83	$206.83	$206.85	$206.80
Purchase #2	$226.38	10.462%	$250.0639	$250.06	$250.05	$250.10
Purchase #3	$98.92	10.696%	$109.5005	$109.50	$109.50	$109.50
Purchase #4	$119.44	8.662%	$129.7859	$129.79	$129.80	$129.80
Purchase #5	$101.69	10.229%	$112.0919	$112.09	$112.10	$112.10
Purchase #6	$157.42	13.779%	$179.1109	$179.11	$179.10	$179.10
Purchase #7	$120.37	5.709%	$127.2419	$127.24	$127.25	$127.20
7 purchase totals =	$1,017.95		$1,114.6250	$1,114.62	$1,114.65	$1,114.60