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	$223.34	8.502%	$242.3284	$242.33	$242.35	$242.30
Purchase #2	$133.92	8.632%	$145.48	$145.48	$145.50	$145.50
Purchase #3	$111.76	13.863%	$127.2533	$127.25	$127.25	$127.30
Purchase #4	$135.29	8.158%	$146.327	$146.33	$146.35	$146.30
Purchase #5	$142.28	10.647%	$157.4286	$157.43	$157.45	$157.40
Purchase #6	$248.99	12.570%	$280.288	$280.29	$280.30	$280.30
Purchase #7	$50.59	7.310%	$54.2881	$54.29	$54.30	$54.30
7 purchase totals =	$1,046.17		$1,153.3934	$1,153.40	$1,153.50	$1,153.40