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	$184.83	10.595%	$204.4127	$204.41	$204.40	$204.40
Purchase #2	$102.35	13.646%	$116.3167	$116.32	$116.30	$116.30
Purchase #3	$72.82	3.693%	$75.5092	$75.51	$75.50	$75.50
Purchase #4	$196.90	13.639%	$223.7552	$223.76	$223.75	$223.80
Purchase #5	$100.41	10.636%	$111.0896	$111.09	$111.10	$111.10
Purchase #6	$199.97	5.405%	$210.7784	$210.78	$210.80	$210.80
Purchase #7	$220.52	13.601%	$250.5129	$250.51	$250.50	$250.50
7 purchase totals =	$1,077.80		$1,192.3747	$1,192.38	$1,192.35	$1,192.40