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	$60.97	10.679%	$67.481	$67.48	$67.50	$67.50
Purchase #2	$171.33	9.854%	$188.2129	$188.21	$188.20	$188.20
Purchase #3	$104.40	7.531%	$112.2624	$112.26	$112.25	$112.30
Purchase #4	$249.98	7.584%	$268.9385	$268.94	$268.95	$268.90
Purchase #5	$240.56	4.249%	$250.7814	$250.78	$250.80	$250.80
Purchase #6	$64.56	9.230%	$70.5189	$70.52	$70.50	$70.50
Purchase #7	$75.33	10.409%	$83.1711	$83.17	$83.15	$83.20
7 purchase totals =	$967.13		$1,041.3662	$1,041.36	$1,041.35	$1,041.40