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	$204.25	3.300%	$210.9903	$210.99	$211.00	$211.00
Purchase #2	$86.50	4.402%	$90.3077	$90.31	$90.30	$90.30
Purchase #3	$86.40	12.270%	$97.0013	$97.00	$97.00	$97.00
Purchase #4	$34.96	8.229%	$37.8369	$37.84	$37.85	$37.80
Purchase #5	$15.82	12.305%	$17.7667	$17.77	$17.75	$17.80
Purchase #6	$155.71	7.400%	$167.2325	$167.23	$167.25	$167.20
Purchase #7	$39.83	7.392%	$42.7742	$42.77	$42.75	$42.80
7 purchase totals =	$623.47		$663.9096	$663.91	$663.90	$663.90