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	$182.83	9.455%	$200.1166	$200.12	$200.10	$200.10
Purchase #2	$90.57	8.732%	$98.4786	$98.48	$98.50	$98.50
Purchase #3	$161.76	7.543%	$173.9616	$173.96	$173.95	$174.00
Purchase #4	$230.67	12.270%	$258.9732	$258.97	$258.95	$259.00
Purchase #5	$116.60	12.279%	$130.9173	$130.92	$130.90	$130.90
Purchase #6	$72.43	8.683%	$78.7191	$78.72	$78.70	$78.70
Purchase #7	$57.91	8.435%	$62.7947	$62.79	$62.80	$62.80
7 purchase totals =	$912.77		$1,003.9611	$1,003.96	$1,003.90	$1,004.00