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	$140.55	6.334%	$149.4524	$149.45	$149.45	$149.50
Purchase #2	$225.82	3.139%	$232.9085	$232.91	$232.90	$232.90
Purchase #3	$240.48	12.436%	$270.3861	$270.39	$270.40	$270.40
Purchase #4	$90.66	10.179%	$99.8883	$99.89	$99.90	$99.90
Purchase #5	$90.62	13.240%	$102.6181	$102.62	$102.60	$102.60
Purchase #6	$37.67	10.167%	$41.4999	$41.50	$41.50	$41.50
Purchase #7	$183.42	8.258%	$198.5668	$198.57	$198.55	$198.60
7 purchase totals =	$1,009.22		$1,095.3201	$1,095.33	$1,095.30	$1,095.40