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	$215.35	7.729%	$231.9944	$231.99	$232.00	$232.00
Purchase #2	$229.75	11.133%	$255.3281	$255.33	$255.35	$255.30
Purchase #3	$198.55	7.446%	$213.334	$213.33	$213.35	$213.30
Purchase #4	$123.99	13.783%	$141.0795	$141.08	$141.10	$141.10
Purchase #5	$10.61	3.505%	$10.9819	$10.98	$11.00	$11.00
Purchase #6	$38.76	10.607%	$42.8713	$42.87	$42.85	$42.90
Purchase #7	$242.31	13.776%	$275.6906	$275.69	$275.70	$275.70
7 purchase totals =	$1,059.32		$1,171.2798	$1,171.27	$1,171.35	$1,171.30