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	$168.32	13.410%	$190.8917	$190.89	$190.90	$190.90
Purchase #2	$52.41	3.596%	$54.2947	$54.29	$54.30	$54.30
Purchase #3	$75.80	13.709%	$86.1914	$86.19	$86.20	$86.20
Purchase #4	$186.59	4.157%	$194.3465	$194.35	$194.35	$194.30
Purchase #5	$79.61	8.610%	$86.4644	$86.46	$86.45	$86.50
Purchase #6	$72.53	11.277%	$80.7092	$80.71	$80.70	$80.70
Purchase #7	$110.38	7.779%	$118.9665	$118.97	$118.95	$119.00
7 purchase totals =	$745.64		$811.8644	$811.86	$811.85	$811.90