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	$49.59	3.526%	$51.3385	$51.34	$51.35	$51.30
Purchase #2	$140.72	9.514%	$154.1081	$154.11	$154.10	$154.10
Purchase #3	$37.79	12.250%	$42.4193	$42.42	$42.40	$42.40
Purchase #4	$219.50	5.679%	$231.9654	$231.97	$231.95	$232.00
Purchase #5	$187.46	3.752%	$194.4935	$194.49	$194.50	$194.50
Purchase #6	$222.60	6.432%	$236.9176	$236.92	$236.90	$236.90
Purchase #7	$126.38	11.811%	$141.3067	$141.31	$141.30	$141.30
7 purchase totals =	$984.04		$1,052.5491	$1,052.56	$1,052.50	$1,052.50