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	$104.93	7.464%	$112.762	$112.76	$112.75	$112.80
Purchase #2	$185.56	11.109%	$206.1739	$206.17	$206.15	$206.20
Purchase #3	$151.86	11.831%	$169.8266	$169.83	$169.85	$169.80
Purchase #4	$130.79	5.153%	$137.5296	$137.53	$137.55	$137.50
Purchase #5	$94.56	4.650%	$98.957	$98.96	$98.95	$99.00
Purchase #6	$214.46	12.397%	$241.0466	$241.05	$241.05	$241.00
Purchase #7	$59.85	3.415%	$61.8939	$61.89	$61.90	$61.90
7 purchase totals =	$942.01		$1,028.1896	$1,028.19	$1,028.20	$1,028.20