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	$39.93	8.591%	$43.3604	$43.36	$43.35	$43.40
Purchase #2	$85.56	12.220%	$96.0154	$96.02	$96.00	$96.00
Purchase #3	$6.54	5.485%	$6.8987	$6.90	$6.90	$6.90
Purchase #4	$79.56	13.613%	$90.3905	$90.39	$90.40	$90.40
Purchase #5	$180.78	7.258%	$193.901	$193.90	$193.90	$193.90
Purchase #6	$123.96	3.610%	$128.435	$128.44	$128.45	$128.40
Purchase #7	$116.41	12.667%	$131.1557	$131.16	$131.15	$131.20
7 purchase totals =	$632.74		$690.1567	$690.17	$690.15	$690.20