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	$163.59	10.595%	$180.9224	$180.92	$180.90	$180.90
Purchase #2	$67.33	8.582%	$73.1083	$73.11	$73.10	$73.10
Purchase #3	$95.87	5.644%	$101.2809	$101.28	$101.30	$101.30
Purchase #4	$86.25	6.862%	$92.1685	$92.17	$92.15	$92.20
Purchase #5	$48.82	13.595%	$55.4571	$55.46	$55.45	$55.50
Purchase #6	$94.63	8.221%	$102.4095	$102.41	$102.40	$102.40
Purchase #7	$241.98	5.481%	$255.2429	$255.24	$255.25	$255.20
7 purchase totals =	$798.47		$860.5896	$860.59	$860.55	$860.60