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	$245.25	9.630%	$268.8676	$268.87	$268.85	$268.90
Purchase #2	$168.57	10.297%	$185.9277	$185.93	$185.95	$185.90
Purchase #3	$188.57	3.130%	$194.4722	$194.47	$194.45	$194.50
Purchase #4	$173.32	13.174%	$196.1532	$196.15	$196.15	$196.20
Purchase #5	$49.50	6.201%	$52.5695	$52.57	$52.55	$52.60
Purchase #6	$107.48	10.787%	$119.0739	$119.07	$119.05	$119.10
Purchase #7	$101.33	13.179%	$114.6843	$114.68	$114.70	$114.70
7 purchase totals =	$1,034.02		$1,131.7484	$1,131.74	$1,131.70	$1,131.90