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	$62.35	4.687%	$65.2723	$65.27	$65.25	$65.30
Purchase #2	$246.72	7.424%	$265.0365	$265.04	$265.05	$265.00
Purchase #3	$246.67	13.450%	$279.8471	$279.85	$279.85	$279.80
Purchase #4	$88.32	5.140%	$92.8596	$92.86	$92.85	$92.90
Purchase #5	$151.64	11.299%	$168.7738	$168.77	$168.75	$168.80
Purchase #6	$72.36	8.363%	$78.4115	$78.41	$78.40	$78.40
Purchase #7	$186.67	3.265%	$192.7648	$192.76	$192.75	$192.80
7 purchase totals =	$1,054.73		$1,142.9656	$1,142.96	$1,142.90	$1,143.00