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	$185.37	8.406%	$200.9522	$200.95	$200.95	$201.00
Purchase #2	$68.79	5.115%	$72.3086	$72.31	$72.30	$72.30
Purchase #3	$245.67	10.377%	$271.1632	$271.16	$271.15	$271.20
Purchase #4	$125.91	13.328%	$142.6913	$142.69	$142.70	$142.70
Purchase #5	$157.34	10.852%	$174.4145	$174.41	$174.40	$174.40
Purchase #6	$76.78	8.727%	$83.4806	$83.48	$83.50	$83.50
Purchase #7	$18.43	10.347%	$20.337	$20.34	$20.35	$20.30
7 purchase totals =	$878.29		$965.3474	$965.34	$965.35	$965.40