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	$80.32	11.460%	$89.5247	$89.52	$89.50	$89.50
Purchase #2	$136.77	4.243%	$142.5732	$142.57	$142.55	$142.60
Purchase #3	$43.35	7.318%	$46.5224	$46.52	$46.50	$46.50
Purchase #4	$240.89	4.787%	$252.4214	$252.42	$252.40	$252.40
Purchase #5	$241.38	4.121%	$251.3273	$251.33	$251.35	$251.30
Purchase #6	$100.42	3.601%	$104.0361	$104.04	$104.05	$104.00
Purchase #7	$228.25	13.406%	$258.8492	$258.85	$258.85	$258.80
7 purchase totals =	$1,071.38		$1,145.2543	$1,145.25	$1,145.20	$1,145.10