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	$218.59	13.745%	$248.6352	$248.64	$248.65	$248.60
Purchase #2	$42.84	3.441%	$44.3141	$44.31	$44.30	$44.30
Purchase #3	$86.55	5.579%	$91.3786	$91.38	$91.40	$91.40
Purchase #4	$71.78	6.656%	$76.5577	$76.56	$76.55	$76.60
Purchase #5	$61.94	5.151%	$65.1305	$65.13	$65.15	$65.10
Purchase #6	$45.29	11.467%	$50.4834	$50.48	$50.50	$50.50
Purchase #7	$188.57	12.186%	$211.5491	$211.55	$211.55	$211.50
7 purchase totals =	$715.56		$788.0486	$788.05	$788.10	$788.00