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	$59.25	3.664%	$61.4209	$61.42	$61.40	$61.40
Purchase #2	$240.42	11.583%	$268.2678	$268.27	$268.25	$268.30
Purchase #3	$67.34	11.323%	$74.9649	$74.96	$74.95	$75.00
Purchase #4	$72.83	11.406%	$81.137	$81.14	$81.15	$81.10
Purchase #5	$180.96	3.613%	$187.4981	$187.50	$187.50	$187.50
Purchase #6	$65.78	5.403%	$69.3341	$69.33	$69.35	$69.30
Purchase #7	$210.76	13.340%	$238.8754	$238.88	$238.90	$238.90
7 purchase totals =	$897.34		$981.4982	$981.50	$981.50	$981.50