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	$78.77	4.202%	$82.0799	$82.08	$82.10	$82.10
Purchase #2	$228.77	4.496%	$239.0555	$239.06	$239.05	$239.10
Purchase #3	$61.87	3.694%	$64.1555	$64.16	$64.15	$64.20
Purchase #4	$87.62	13.304%	$99.277	$99.28	$99.30	$99.30
Purchase #5	$142.93	3.815%	$148.3828	$148.38	$148.40	$148.40
Purchase #6	$86.47	3.692%	$89.6625	$89.66	$89.65	$89.70
Purchase #7	$66.86	8.327%	$72.4274	$72.43	$72.45	$72.40
7 purchase totals =	$753.29		$795.0406	$795.05	$795.10	$795.20