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	$228.53	10.816%	$253.2478	$253.25	$253.25	$253.20
Purchase #2	$28.42	13.376%	$32.2215	$32.22	$32.20	$32.20
Purchase #3	$229.49	3.429%	$237.3592	$237.36	$237.35	$237.40
Purchase #4	$116.37	12.681%	$131.1269	$131.13	$131.15	$131.10
Purchase #5	$154.91	6.459%	$164.9156	$164.92	$164.90	$164.90
Purchase #6	$152.56	9.650%	$167.282	$167.28	$167.30	$167.30
Purchase #7	$183.42	6.121%	$194.6471	$194.65	$194.65	$194.60
7 purchase totals =	$1,093.70		$1,180.8001	$1,180.81	$1,180.80	$1,180.70