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	$236.44	3.362%	$244.3891	$244.39	$244.40	$244.40
Purchase #2	$223.32	7.620%	$240.337	$240.34	$240.35	$240.30
Purchase #3	$58.68	10.862%	$65.0538	$65.05	$65.05	$65.10
Purchase #4	$180.96	8.640%	$196.5949	$196.59	$196.60	$196.60
Purchase #5	$179.85	9.437%	$196.8224	$196.82	$196.80	$196.80
Purchase #6	$153.49	6.694%	$163.7646	$163.76	$163.75	$163.80
Purchase #7	$91.30	11.656%	$101.9419	$101.94	$101.95	$101.90
7 purchase totals =	$1,124.04		$1,208.9037	$1,208.89	$1,208.90	$1,208.90