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	$42.39	6.836%	$45.2878	$45.29	$45.30	$45.30
Purchase #2	$107.57	3.560%	$111.3995	$111.40	$111.40	$111.40
Purchase #3	$46.46	3.562%	$48.1149	$48.11	$48.10	$48.10
Purchase #4	$52.82	12.264%	$59.2978	$59.30	$59.30	$59.30
Purchase #5	$79.34	4.329%	$82.7746	$82.77	$82.75	$82.80
Purchase #6	$182.34	3.159%	$188.1001	$188.10	$188.10	$188.10
Purchase #7	$236.79	10.277%	$261.1249	$261.12	$261.10	$261.10
7 purchase totals =	$747.71		$796.0996	$796.09	$796.05	$796.10