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	$42.33	4.401%	$44.1929	$44.19	$44.20	$44.20
Purchase #2	$115.54	3.503%	$119.5874	$119.59	$119.60	$119.60
Purchase #3	$48.48	13.483%	$55.0166	$55.02	$55.00	$55.00
Purchase #4	$200.65	11.781%	$224.2886	$224.29	$224.30	$224.30
Purchase #5	$229.66	3.623%	$237.9806	$237.98	$238.00	$238.00
Purchase #6	$100.33	4.856%	$105.202	$105.20	$105.20	$105.20
Purchase #7	$111.90	10.642%	$123.8084	$123.81	$123.80	$123.80
7 purchase totals =	$848.89		$910.0765	$910.08	$910.10	$910.10