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	$248.86	4.318%	$259.6058	$259.61	$259.60	$259.60
Purchase #2	$70.42	13.858%	$80.1788	$80.18	$80.20	$80.20
Purchase #3	$179.88	6.122%	$190.8923	$190.89	$190.90	$190.90
Purchase #4	$49.71	6.510%	$52.9461	$52.95	$52.95	$52.90
Purchase #5	$57.92	3.270%	$59.814	$59.81	$59.80	$59.80
Purchase #6	$190.32	4.596%	$199.0671	$199.07	$199.05	$199.10
Purchase #7	$196.32	6.486%	$209.0533	$209.05	$209.05	$209.10
7 purchase totals =	$993.43		$1,051.5574	$1,051.56	$1,051.55	$1,051.60