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	$180.89	8.161%	$195.6524	$195.65	$195.65	$195.70
Purchase #2	$42.83	6.364%	$45.5557	$45.56	$45.55	$45.60
Purchase #3	$172.70	7.691%	$185.9824	$185.98	$186.00	$186.00
Purchase #4	$113.86	9.669%	$124.8691	$124.87	$124.85	$124.90
Purchase #5	$111.41	10.712%	$123.3442	$123.34	$123.35	$123.30
Purchase #6	$154.58	9.535%	$169.3192	$169.32	$169.30	$169.30
Purchase #7	$93.64	8.628%	$101.7193	$101.72	$101.70	$101.70
7 purchase totals =	$869.91		$946.4423	$946.44	$946.40	$946.50