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	$34.63	9.330%	$37.861	$37.86	$37.85	$37.90
Purchase #2	$88.91	10.231%	$98.0064	$98.01	$98.00	$98.00
Purchase #3	$248.80	10.768%	$275.5908	$275.59	$275.60	$275.60
Purchase #4	$217.87	11.780%	$243.5351	$243.54	$243.55	$243.50
Purchase #5	$9.70	12.512%	$10.9137	$10.91	$10.90	$10.90
Purchase #6	$108.43	5.548%	$114.4457	$114.45	$114.45	$114.40
Purchase #7	$42.85	9.409%	$46.8818	$46.88	$46.90	$46.90
7 purchase totals =	$751.19		$827.2345	$827.24	$827.25	$827.20