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	$215.69	11.862%	$241.2751	$241.28	$241.30	$241.30
Purchase #2	$77.28	3.773%	$80.1958	$80.20	$80.20	$80.20
Purchase #3	$89.33	13.398%	$101.2984	$101.30	$101.30	$101.30
Purchase #4	$120.51	8.710%	$131.0064	$131.01	$131.00	$131.00
Purchase #5	$146.70	3.809%	$152.2878	$152.29	$152.30	$152.30
Purchase #6	$33.99	5.812%	$35.9655	$35.97	$35.95	$36.00
Purchase #7	$126.62	12.467%	$142.4057	$142.41	$142.40	$142.40
7 purchase totals =	$810.12		$884.4347	$884.46	$884.45	$884.50