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	$73.96	11.349%	$82.3537	$82.35	$82.35	$82.40
Purchase #2	$16.56	11.495%	$18.4636	$18.46	$18.45	$18.50
Purchase #3	$82.45	7.413%	$88.562	$88.56	$88.55	$88.60
Purchase #4	$33.49	4.586%	$35.0259	$35.03	$35.05	$35.00
Purchase #5	$75.44	13.745%	$85.8092	$85.81	$85.80	$85.80
Purchase #6	$137.56	13.723%	$156.4374	$156.44	$156.45	$156.40
Purchase #7	$200.85	5.149%	$211.1918	$211.19	$211.20	$211.20
7 purchase totals =	$620.31		$677.8436	$677.84	$677.85	$677.90