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	$15.75	4.514%	$16.461	$16.46	$16.45	$16.50
Purchase #2	$137.36	3.799%	$142.5783	$142.58	$142.60	$142.60
Purchase #3	$241.92	10.371%	$267.0095	$267.01	$267.00	$267.00
Purchase #4	$176.81	4.874%	$185.4277	$185.43	$185.45	$185.40
Purchase #5	$139.44	6.408%	$148.3753	$148.38	$148.40	$148.40
Purchase #6	$190.89	12.834%	$215.3888	$215.39	$215.40	$215.40
Purchase #7	$161.33	3.771%	$167.4138	$167.41	$167.40	$167.40
7 purchase totals =	$1,063.50		$1,142.6544	$1,142.66	$1,142.70	$1,142.70