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	$82.81	9.250%	$90.4699	$90.47	$90.45	$90.50
Purchase #2	$49.51	5.428%	$52.1974	$52.20	$52.20	$52.20
Purchase #3	$220.35	12.685%	$248.3014	$248.30	$248.30	$248.30
Purchase #4	$174.51	3.796%	$181.1344	$181.13	$181.15	$181.10
Purchase #5	$92.85	5.144%	$97.6262	$97.63	$97.65	$97.60
Purchase #6	$185.26	12.304%	$208.0544	$208.05	$208.05	$208.10
Purchase #7	$173.54	3.173%	$179.0464	$179.05	$179.05	$179.00
7 purchase totals =	$978.83		$1,056.8301	$1,056.83	$1,056.85	$1,056.80