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	$162.38	6.416%	$172.7983	$172.80	$172.80	$172.80
Purchase #2	$52.80	5.286%	$55.591	$55.59	$55.60	$55.60
Purchase #3	$40.25	6.266%	$42.7721	$42.77	$42.75	$42.80
Purchase #4	$51.41	12.414%	$57.792	$57.79	$57.80	$57.80
Purchase #5	$235.69	6.254%	$250.4301	$250.43	$250.45	$250.40
Purchase #6	$227.34	6.457%	$242.0193	$242.02	$242.00	$242.00
Purchase #7	$87.47	8.367%	$94.7886	$94.79	$94.80	$94.80
7 purchase totals =	$857.34		$916.1914	$916.19	$916.20	$916.20