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	$92.98	4.728%	$97.3761	$97.38	$97.40	$97.40
Purchase #2	$196.81	9.848%	$216.1918	$216.19	$216.20	$216.20
Purchase #3	$152.92	9.501%	$167.4489	$167.45	$167.45	$167.40
Purchase #4	$40.98	12.806%	$46.2279	$46.23	$46.25	$46.20
Purchase #5	$33.99	4.485%	$35.5145	$35.51	$35.50	$35.50
Purchase #6	$186.90	9.833%	$205.2779	$205.28	$205.30	$205.30
Purchase #7	$186.77	12.647%	$210.3908	$210.39	$210.40	$210.40
7 purchase totals =	$891.35		$978.4279	$978.43	$978.50	$978.40