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	$244.85	11.386%	$272.7286	$272.73	$272.75	$272.70
Purchase #2	$141.54	10.445%	$156.3239	$156.32	$156.30	$156.30
Purchase #3	$203.32	11.667%	$227.0413	$227.04	$227.05	$227.00
Purchase #4	$79.38	11.657%	$88.6333	$88.63	$88.65	$88.60
Purchase #5	$104.46	4.835%	$109.5106	$109.51	$109.50	$109.50
Purchase #6	$158.32	11.256%	$176.1405	$176.14	$176.15	$176.10
Purchase #7	$158.51	8.802%	$172.4621	$172.46	$172.45	$172.50
7 purchase totals =	$1,090.38		$1,202.8403	$1,202.83	$1,202.85	$1,202.70