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	$208.79	13.288%	$236.534	$236.53	$236.55	$236.50
Purchase #2	$95.97	3.584%	$99.4096	$99.41	$99.40	$99.40
Purchase #3	$6.48	11.405%	$7.219	$7.22	$7.20	$7.20
Purchase #4	$183.37	6.553%	$195.3862	$195.39	$195.40	$195.40
Purchase #5	$58.51	13.508%	$66.4135	$66.41	$66.40	$66.40
Purchase #6	$81.88	9.179%	$89.3958	$89.40	$89.40	$89.40
Purchase #7	$96.49	5.527%	$101.823	$101.82	$101.80	$101.80
7 purchase totals =	$731.49		$796.1811	$796.18	$796.15	$796.10