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	$93.71	13.669%	$106.5192	$106.52	$106.50	$106.50
Purchase #2	$92.32	4.285%	$96.2759	$96.28	$96.30	$96.30
Purchase #3	$51.90	7.440%	$55.7614	$55.76	$55.75	$55.80
Purchase #4	$236.27	8.538%	$256.4427	$256.44	$256.45	$256.40
Purchase #5	$248.78	13.158%	$281.5145	$281.51	$281.50	$281.50
Purchase #6	$248.54	4.449%	$259.5975	$259.60	$259.60	$259.60
Purchase #7	$38.67	4.492%	$40.4071	$40.41	$40.40	$40.40
7 purchase totals =	$1,010.19		$1,096.5183	$1,096.52	$1,096.50	$1,096.50