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	$95.52	7.229%	$102.4251	$102.43	$102.45	$102.40
Purchase #2	$96.48	5.113%	$101.413	$101.41	$101.40	$101.40
Purchase #3	$244.64	13.718%	$278.1997	$278.20	$278.20	$278.20
Purchase #4	$9.51	6.320%	$10.111	$10.11	$10.10	$10.10
Purchase #5	$202.46	6.608%	$215.8386	$215.84	$215.85	$215.80
Purchase #6	$85.83	10.477%	$94.8224	$94.82	$94.80	$94.80
Purchase #7	$51.71	3.531%	$53.5359	$53.54	$53.55	$53.50
7 purchase totals =	$786.15		$856.3457	$856.35	$856.35	$856.20