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	$114.77	11.127%	$127.5405	$127.54	$127.55	$127.50
Purchase #2	$29.41	8.858%	$32.0151	$32.02	$32.00	$32.00
Purchase #3	$141.56	4.761%	$148.2997	$148.30	$148.30	$148.30
Purchase #4	$169.86	7.633%	$182.8254	$182.83	$182.85	$182.80
Purchase #5	$234.91	8.492%	$254.8586	$254.86	$254.85	$254.90
Purchase #6	$196.37	10.158%	$216.3173	$216.32	$216.30	$216.30
Purchase #7	$14.30	7.157%	$15.3235	$15.32	$15.30	$15.30
7 purchase totals =	$901.18		$977.1801	$977.19	$977.15	$977.10