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	$248.66	9.542%	$272.3871	$272.39	$272.40	$272.40
Purchase #2	$56.92	3.854%	$59.1137	$59.11	$59.10	$59.10
Purchase #3	$91.85	7.752%	$98.9702	$98.97	$98.95	$99.00
Purchase #4	$169.25	3.406%	$175.0147	$175.01	$175.00	$175.00
Purchase #5	$186.46	6.869%	$199.2679	$199.27	$199.25	$199.30
Purchase #6	$81.53	4.526%	$85.22	$85.22	$85.20	$85.20
Purchase #7	$232.42	13.806%	$264.5079	$264.51	$264.50	$264.50
7 purchase totals =	$1,067.09		$1,154.4815	$1,154.48	$1,154.40	$1,154.50