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	$37.98	10.375%	$41.9204	$41.92	$41.90	$41.90
Purchase #2	$116.68	10.371%	$128.7809	$128.78	$128.80	$128.80
Purchase #3	$46.41	12.704%	$52.3059	$52.31	$52.30	$52.30
Purchase #4	$169.42	5.552%	$178.8262	$178.83	$178.85	$178.80
Purchase #5	$182.71	7.699%	$196.7768	$196.78	$196.80	$196.80
Purchase #6	$195.81	13.173%	$221.6041	$221.60	$221.60	$221.60
Purchase #7	$239.31	10.723%	$264.9712	$264.97	$264.95	$265.00
7 purchase totals =	$988.32		$1,085.1855	$1,085.19	$1,085.20	$1,085.20