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	$168.33	5.511%	$177.6067	$177.61	$177.60	$177.60
Purchase #2	$87.83	8.638%	$95.4168	$95.42	$95.40	$95.40
Purchase #3	$165.44	4.146%	$172.2991	$172.30	$172.30	$172.30
Purchase #4	$55.41	6.824%	$59.1912	$59.19	$59.20	$59.20
Purchase #5	$225.56	12.854%	$254.5535	$254.55	$254.55	$254.60
Purchase #6	$120.80	12.233%	$135.5775	$135.58	$135.60	$135.60
Purchase #7	$117.92	5.384%	$124.2688	$124.27	$124.25	$124.30
7 purchase totals =	$941.29		$1,018.9136	$1,018.92	$1,018.90	$1,019.00