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	$58.52	7.457%	$62.8838	$62.88	$62.90	$62.90
Purchase #2	$149.26	12.826%	$168.4041	$168.40	$168.40	$168.40
Purchase #3	$77.40	13.588%	$87.9171	$87.92	$87.90	$87.90
Purchase #4	$202.90	6.845%	$216.7885	$216.79	$216.80	$216.80
Purchase #5	$77.94	5.874%	$82.5182	$82.52	$82.50	$82.50
Purchase #6	$77.30	10.368%	$85.3145	$85.31	$85.30	$85.30
Purchase #7	$9.26	13.198%	$10.4821	$10.48	$10.50	$10.50
7 purchase totals =	$652.58		$714.3083	$714.30	$714.30	$714.30