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	$174.47	5.602%	$184.2438	$184.24	$184.25	$184.20
Purchase #2	$204.58	6.303%	$217.4747	$217.47	$217.45	$217.50
Purchase #3	$215.53	7.853%	$232.4556	$232.46	$232.45	$232.50
Purchase #4	$95.91	10.405%	$105.8894	$105.89	$105.90	$105.90
Purchase #5	$53.73	4.119%	$55.9431	$55.94	$55.95	$55.90
Purchase #6	$208.29	7.864%	$224.6699	$224.67	$224.65	$224.70
Purchase #7	$138.94	8.154%	$150.2692	$150.27	$150.25	$150.30
7 purchase totals =	$1,091.45		$1,170.9457	$1,170.94	$1,170.90	$1,171.00