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	$232.25	13.697%	$264.0613	$264.06	$264.05	$264.10
Purchase #2	$75.52	10.279%	$83.2827	$83.28	$83.30	$83.30
Purchase #3	$151.45	7.321%	$162.5377	$162.54	$162.55	$162.50
Purchase #4	$103.88	13.651%	$118.0607	$118.06	$118.05	$118.10
Purchase #5	$129.39	11.185%	$143.8623	$143.86	$143.85	$143.90
Purchase #6	$229.38	7.379%	$246.306	$246.31	$246.30	$246.30
Purchase #7	$51.84	6.609%	$55.2661	$55.27	$55.25	$55.30
7 purchase totals =	$973.71		$1,073.3768	$1,073.38	$1,073.35	$1,073.50