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	$157.56	10.612%	$174.2803	$174.28	$174.30	$174.30
Purchase #2	$78.78	10.279%	$86.8778	$86.88	$86.90	$86.90
Purchase #3	$192.50	13.765%	$218.9976	$219.00	$219.00	$219.00
Purchase #4	$189.53	7.366%	$203.4908	$203.49	$203.50	$203.50
Purchase #5	$104.28	5.314%	$109.8214	$109.82	$109.80	$109.80
Purchase #6	$238.60	13.861%	$271.6723	$271.67	$271.65	$271.70
Purchase #7	$99.59	3.152%	$102.7291	$102.73	$102.75	$102.70
7 purchase totals =	$1,060.84		$1,167.8693	$1,167.87	$1,167.90	$1,167.90