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	$49.66	8.393%	$53.828	$53.83	$53.85	$53.80
Purchase #2	$215.44	10.402%	$237.8501	$237.85	$237.85	$237.90
Purchase #3	$136.89	10.671%	$151.4975	$151.50	$151.50	$151.50
Purchase #4	$105.64	13.489%	$119.8898	$119.89	$119.90	$119.90
Purchase #5	$18.80	10.532%	$20.78	$20.78	$20.80	$20.80
Purchase #6	$131.72	11.873%	$147.3591	$147.36	$147.35	$147.40
Purchase #7	$63.63	8.437%	$68.9985	$69.00	$69.00	$69.00
7 purchase totals =	$721.78		$800.2030	$800.21	$800.25	$800.30