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	$216.32	5.118%	$227.3913	$227.39	$227.40	$227.40
Purchase #2	$115.38	8.677%	$125.3915	$125.39	$125.40	$125.40
Purchase #3	$147.35	11.515%	$164.3174	$164.32	$164.30	$164.30
Purchase #4	$147.71	13.136%	$167.1132	$167.11	$167.10	$167.10
Purchase #5	$69.46	3.491%	$71.8848	$71.88	$71.90	$71.90
Purchase #6	$79.76	9.476%	$87.3181	$87.32	$87.30	$87.30
Purchase #7	$82.40	8.789%	$89.6421	$89.64	$89.65	$89.60
7 purchase totals =	$858.38		$933.0584	$933.05	$933.05	$933.00