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	$100.82	3.108%	$103.9535	$103.95	$103.95	$104.00
Purchase #2	$190.87	12.651%	$215.017	$215.02	$215.00	$215.00
Purchase #3	$134.43	13.661%	$152.7945	$152.79	$152.80	$152.80
Purchase #4	$130.82	7.176%	$140.2076	$140.21	$140.20	$140.20
Purchase #5	$65.32	7.803%	$70.4169	$70.42	$70.40	$70.40
Purchase #6	$210.89	8.355%	$228.5099	$228.51	$228.50	$228.50
Purchase #7	$99.86	7.460%	$107.3096	$107.31	$107.30	$107.30
7 purchase totals =	$933.01		$1,018.2090	$1,018.21	$1,018.15	$1,018.20