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	$220.92	3.212%	$228.016	$228.02	$228.00	$228.00
Purchase #2	$62.71	5.728%	$66.302	$66.30	$66.30	$66.30
Purchase #3	$152.50	7.604%	$164.0961	$164.10	$164.10	$164.10
Purchase #4	$212.79	6.362%	$226.3277	$226.33	$226.35	$226.30
Purchase #5	$129.63	9.796%	$142.3286	$142.33	$142.35	$142.30
Purchase #6	$40.77	12.384%	$45.819	$45.82	$45.80	$45.80
Purchase #7	$105.34	6.758%	$112.4589	$112.46	$112.45	$112.50
7 purchase totals =	$924.66		$985.3483	$985.36	$985.35	$985.30