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	$35.28	7.330%	$37.866	$37.87	$37.85	$37.90
Purchase #2	$90.75	9.757%	$99.6045	$99.60	$99.60	$99.60
Purchase #3	$205.31	11.200%	$228.3047	$228.30	$228.30	$228.30
Purchase #4	$83.30	5.817%	$88.1456	$88.15	$88.15	$88.10
Purchase #5	$213.72	6.776%	$228.2017	$228.20	$228.20	$228.20
Purchase #6	$159.57	11.297%	$177.5966	$177.60	$177.60	$177.60
Purchase #7	$137.39	3.600%	$142.336	$142.34	$142.35	$142.30
7 purchase totals =	$925.32		$1,002.0551	$1,002.06	$1,002.05	$1,002.00