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	$237.89	11.162%	$264.4433	$264.44	$264.45	$264.40
Purchase #2	$37.25	13.408%	$42.2445	$42.24	$42.25	$42.20
Purchase #3	$194.88	3.839%	$202.3614	$202.36	$202.35	$202.40
Purchase #4	$48.38	9.373%	$52.9147	$52.91	$52.90	$52.90
Purchase #5	$249.76	6.731%	$266.5713	$266.57	$266.55	$266.60
Purchase #6	$192.40	8.336%	$208.4385	$208.44	$208.45	$208.40
Purchase #7	$63.71	4.405%	$66.5164	$66.52	$66.50	$66.50
7 purchase totals =	$1,024.27		$1,103.4901	$1,103.48	$1,103.45	$1,103.40