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	$157.80	11.140%	$175.3789	$175.38	$175.40	$175.40
Purchase #2	$42.32	12.480%	$47.6015	$47.60	$47.60	$47.60
Purchase #3	$84.51	8.242%	$91.4753	$91.48	$91.50	$91.50
Purchase #4	$114.57	8.125%	$123.8788	$123.88	$123.90	$123.90
Purchase #5	$234.85	8.357%	$254.4764	$254.48	$254.50	$254.50
Purchase #6	$127.37	11.805%	$142.406	$142.41	$142.40	$142.40
Purchase #7	$31.87	12.822%	$35.9564	$35.96	$35.95	$36.00
7 purchase totals =	$793.29		$871.1733	$871.19	$871.25	$871.30