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	$108.29	3.554%	$112.1386	$112.14	$112.15	$112.10
Purchase #2	$178.33	3.693%	$184.9157	$184.92	$184.90	$184.90
Purchase #3	$38.79	9.262%	$42.3827	$42.38	$42.40	$42.40
Purchase #4	$22.55	8.165%	$24.3912	$24.39	$24.40	$24.40
Purchase #5	$58.99	9.382%	$64.5244	$64.52	$64.50	$64.50
Purchase #6	$142.91	6.309%	$151.9262	$151.93	$151.95	$151.90
Purchase #7	$70.57	11.561%	$78.7286	$78.73	$78.75	$78.70
7 purchase totals =	$620.43		$659.0074	$659.01	$659.05	$658.90