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	$164.53	4.218%	$171.4699	$171.47	$171.45	$171.50
Purchase #2	$137.43	6.117%	$145.8366	$145.84	$145.85	$145.80
Purchase #3	$28.35	6.870%	$30.2976	$30.30	$30.30	$30.30
Purchase #4	$175.84	5.228%	$185.0329	$185.03	$185.05	$185.00
Purchase #5	$169.94	10.805%	$188.302	$188.30	$188.30	$188.30
Purchase #6	$42.83	3.841%	$44.4751	$44.48	$44.50	$44.50
Purchase #7	$214.90	10.388%	$237.2238	$237.22	$237.20	$237.20
7 purchase totals =	$933.82		$1,002.6379	$1,002.64	$1,002.65	$1,002.60