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	$206.89	4.538%	$216.2787	$216.28	$216.30	$216.30
Purchase #2	$73.34	6.533%	$78.1313	$78.13	$78.15	$78.10
Purchase #3	$114.41	9.639%	$125.438	$125.44	$125.45	$125.40
Purchase #4	$6.94	4.650%	$7.2627	$7.26	$7.25	$7.30
Purchase #5	$173.69	10.303%	$191.5853	$191.59	$191.60	$191.60
Purchase #6	$165.91	3.626%	$171.9259	$171.93	$171.95	$171.90
Purchase #7	$112.38	5.610%	$118.6845	$118.68	$118.70	$118.70
7 purchase totals =	$853.56		$909.3064	$909.31	$909.40	$909.30