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	$96.81	3.460%	$100.1596	$100.16	$100.15	$100.20
Purchase #2	$151.25	4.169%	$157.5556	$157.56	$157.55	$157.60
Purchase #3	$42.57	6.677%	$45.4124	$45.41	$45.40	$45.40
Purchase #4	$75.57	11.547%	$84.2961	$84.30	$84.30	$84.30
Purchase #5	$108.82	7.418%	$116.8923	$116.89	$116.90	$116.90
Purchase #6	$225.60	3.329%	$233.1102	$233.11	$233.10	$233.10
Purchase #7	$156.73	3.476%	$162.1779	$162.18	$162.20	$162.20
7 purchase totals =	$857.35		$899.6041	$899.61	$899.60	$899.70