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	$196.36	4.653%	$205.4966	$205.50	$205.50	$205.50
Purchase #2	$148.76	5.470%	$156.8972	$156.90	$156.90	$156.90
Purchase #3	$19.94	6.692%	$21.2744	$21.27	$21.25	$21.30
Purchase #4	$224.86	9.259%	$245.6798	$245.68	$245.70	$245.70
Purchase #5	$22.97	10.665%	$25.4198	$25.42	$25.40	$25.40
Purchase #6	$86.85	10.798%	$96.2281	$96.23	$96.25	$96.20
Purchase #7	$78.31	5.394%	$82.534	$82.53	$82.55	$82.50
7 purchase totals =	$778.05		$833.5299	$833.53	$833.55	$833.50