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	$58.70	12.164%	$65.8403	$65.84	$65.85	$65.80
Purchase #2	$42.68	5.474%	$45.0163	$45.02	$45.00	$45.00
Purchase #3	$105.31	9.507%	$115.3218	$115.32	$115.30	$115.30
Purchase #4	$158.86	12.735%	$179.0908	$179.09	$179.10	$179.10
Purchase #5	$181.65	10.571%	$200.8522	$200.85	$200.85	$200.90
Purchase #6	$128.28	11.700%	$143.2888	$143.29	$143.30	$143.30
Purchase #7	$99.70	12.480%	$112.1426	$112.14	$112.15	$112.10
7 purchase totals =	$775.18		$861.5528	$861.55	$861.55	$861.50