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	$206.29	3.347%	$213.1945	$213.19	$213.20	$213.20
Purchase #2	$71.34	10.312%	$78.6966	$78.70	$78.70	$78.70
Purchase #3	$186.33	5.446%	$196.4775	$196.48	$196.50	$196.50
Purchase #4	$152.49	5.269%	$160.5247	$160.52	$160.50	$160.50
Purchase #5	$123.65	6.108%	$131.2025	$131.20	$131.20	$131.20
Purchase #6	$208.51	5.167%	$219.2837	$219.28	$219.30	$219.30
Purchase #7	$76.31	12.722%	$86.0182	$86.02	$86.00	$86.00
7 purchase totals =	$1,024.92		$1,085.3977	$1,085.39	$1,085.40	$1,085.40