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	$87.75	10.231%	$96.7277	$96.73	$96.75	$96.70
Purchase #2	$142.75	5.577%	$150.7112	$150.71	$150.70	$150.70
Purchase #3	$111.46	12.870%	$125.8049	$125.80	$125.80	$125.80
Purchase #4	$125.47	11.717%	$140.1713	$140.17	$140.15	$140.20
Purchase #5	$140.26	3.383%	$145.005	$145.01	$145.00	$145.00
Purchase #6	$39.30	10.472%	$43.4155	$43.42	$43.40	$43.40
Purchase #7	$114.25	11.758%	$127.6835	$127.68	$127.70	$127.70
7 purchase totals =	$761.24		$829.5191	$829.52	$829.50	$829.50