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	$148.61	9.322%	$162.4634	$162.46	$162.45	$162.50
Purchase #2	$240.63	4.259%	$250.8784	$250.88	$250.90	$250.90
Purchase #3	$177.32	7.323%	$190.3051	$190.31	$190.30	$190.30
Purchase #4	$175.26	8.494%	$190.1466	$190.15	$190.15	$190.10
Purchase #5	$83.51	4.720%	$87.4517	$87.45	$87.45	$87.50
Purchase #6	$62.51	6.383%	$66.5	$66.50	$66.50	$66.50
Purchase #7	$184.67	7.629%	$198.7585	$198.76	$198.75	$198.80
7 purchase totals =	$1,072.51		$1,146.5037	$1,146.51	$1,146.50	$1,146.60