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	$46.29	4.434%	$48.3425	$48.34	$48.35	$48.30
Purchase #2	$172.29	10.467%	$190.3236	$190.32	$190.30	$190.30
Purchase #3	$47.55	13.791%	$54.1076	$54.11	$54.10	$54.10
Purchase #4	$136.85	4.321%	$142.7633	$142.76	$142.75	$142.80
Purchase #5	$157.38	6.188%	$167.1187	$167.12	$167.10	$167.10
Purchase #6	$217.85	8.509%	$236.3869	$236.39	$236.40	$236.40
Purchase #7	$156.32	5.340%	$164.6675	$164.67	$164.65	$164.70
7 purchase totals =	$934.53		$1,003.7101	$1,003.71	$1,003.65	$1,003.70