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	$56.74	5.566%	$59.8981	$59.90	$59.90	$59.90
Purchase #2	$175.33	9.495%	$191.9776	$191.98	$192.00	$192.00
Purchase #3	$7.34	13.193%	$8.3084	$8.31	$8.30	$8.30
Purchase #4	$192.51	7.174%	$206.3207	$206.32	$206.30	$206.30
Purchase #5	$59.37	8.677%	$64.5215	$64.52	$64.50	$64.50
Purchase #6	$232.71	13.461%	$264.0351	$264.04	$264.05	$264.00
Purchase #7	$250.92	4.591%	$262.4397	$262.44	$262.45	$262.40
7 purchase totals =	$974.92		$1,057.5011	$1,057.51	$1,057.50	$1,057.40