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	$135.65	12.617%	$152.765	$152.77	$152.75	$152.80
Purchase #2	$46.92	13.820%	$53.4043	$53.40	$53.40	$53.40
Purchase #3	$73.85	5.425%	$77.8564	$77.86	$77.85	$77.90
Purchase #4	$24.59	4.412%	$25.6749	$25.67	$25.65	$25.70
Purchase #5	$132.61	8.760%	$144.2266	$144.23	$144.25	$144.20
Purchase #6	$150.41	9.477%	$164.6644	$164.66	$164.65	$164.70
Purchase #7	$121.83	5.318%	$128.3089	$128.31	$128.30	$128.30
7 purchase totals =	$685.86		$746.9005	$746.90	$746.85	$747.00