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	$208.82	13.572%	$237.1611	$237.16	$237.15	$237.20
Purchase #2	$45.77	7.490%	$49.1982	$49.20	$49.20	$49.20
Purchase #3	$63.57	3.683%	$65.9113	$65.91	$65.90	$65.90
Purchase #4	$162.52	7.374%	$174.5042	$174.50	$174.50	$174.50
Purchase #5	$82.39	8.622%	$89.4937	$89.49	$89.50	$89.50
Purchase #6	$16.53	12.552%	$18.6048	$18.60	$18.60	$18.60
Purchase #7	$180.44	3.614%	$186.9611	$186.96	$186.95	$187.00
7 purchase totals =	$760.04		$821.8344	$821.82	$821.80	$821.90