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	$36.54	12.673%	$41.1707	$41.17	$41.15	$41.20
Purchase #2	$53.67	5.233%	$56.4786	$56.48	$56.50	$56.50
Purchase #3	$75.88	9.503%	$83.0909	$83.09	$83.10	$83.10
Purchase #4	$18.33	4.168%	$19.094	$19.09	$19.10	$19.10
Purchase #5	$215.75	10.710%	$238.8568	$238.86	$238.85	$238.90
Purchase #6	$57.38	3.507%	$59.3923	$59.39	$59.40	$59.40
Purchase #7	$98.43	12.474%	$110.7082	$110.71	$110.70	$110.70
7 purchase totals =	$555.98		$608.7915	$608.79	$608.80	$608.90