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	$52.74	8.693%	$57.3247	$57.32	$57.30	$57.30
Purchase #2	$95.55	6.128%	$101.4053	$101.41	$101.40	$101.40
Purchase #3	$101.27	8.133%	$109.5063	$109.51	$109.50	$109.50
Purchase #4	$147.50	10.121%	$162.4285	$162.43	$162.45	$162.40
Purchase #5	$227.98	12.115%	$255.5998	$255.60	$255.60	$255.60
Purchase #6	$102.30	4.202%	$106.5986	$106.60	$106.60	$106.60
Purchase #7	$247.59	8.692%	$269.1105	$269.11	$269.10	$269.10
7 purchase totals =	$974.93		$1,061.9737	$1,061.98	$1,061.95	$1,061.90