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	$220.32	9.761%	$241.8254	$241.83	$241.85	$241.80
Purchase #2	$155.30	11.611%	$173.3319	$173.33	$173.35	$173.30
Purchase #3	$41.38	10.210%	$45.6049	$45.60	$45.60	$45.60
Purchase #4	$46.61	4.770%	$48.8333	$48.83	$48.85	$48.80
Purchase #5	$229.62	6.351%	$244.2032	$244.20	$244.20	$244.20
Purchase #6	$199.26	6.645%	$212.5008	$212.50	$212.50	$212.50
Purchase #7	$134.42	3.819%	$139.5535	$139.55	$139.55	$139.60
7 purchase totals =	$1,026.91		$1,105.8530	$1,105.84	$1,105.90	$1,105.80