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	$36.94	10.398%	$40.781	$40.78	$40.80	$40.80
Purchase #2	$85.77	10.787%	$95.022	$95.02	$95.00	$95.00
Purchase #3	$96.99	5.713%	$102.531	$102.53	$102.55	$102.50
Purchase #4	$150.45	11.260%	$167.3907	$167.39	$167.40	$167.40
Purchase #5	$10.85	4.161%	$11.3015	$11.30	$11.30	$11.30
Purchase #6	$30.80	4.874%	$32.3012	$32.30	$32.30	$32.30
Purchase #7	$23.59	9.662%	$25.8693	$25.87	$25.85	$25.90
7 purchase totals =	$435.39		$475.1967	$475.19	$475.20	$475.20