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	$35.44	4.846%	$37.1574	$37.16	$37.15	$37.20
Purchase #2	$135.74	9.812%	$149.0588	$149.06	$149.05	$149.10
Purchase #3	$144.27	4.166%	$150.2803	$150.28	$150.30	$150.30
Purchase #4	$233.53	9.831%	$256.4883	$256.49	$256.50	$256.50
Purchase #5	$169.94	8.859%	$184.995	$185.00	$185.00	$185.00
Purchase #6	$104.86	4.309%	$109.3784	$109.38	$109.40	$109.40
Purchase #7	$165.60	5.341%	$174.4447	$174.44	$174.45	$174.40
7 purchase totals =	$989.38		$1,061.8029	$1,061.81	$1,061.85	$1,061.90