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	$43.55	5.145%	$45.7906	$45.79	$45.80	$45.80
Purchase #2	$167.66	12.654%	$188.8757	$188.88	$188.90	$188.90
Purchase #3	$177.72	6.644%	$189.5277	$189.53	$189.55	$189.50
Purchase #4	$168.37	6.393%	$179.1339	$179.13	$179.15	$179.10
Purchase #5	$167.51	7.859%	$180.6746	$180.67	$180.65	$180.70
Purchase #6	$74.25	3.329%	$76.7218	$76.72	$76.70	$76.70
Purchase #7	$168.80	3.435%	$174.5983	$174.60	$174.60	$174.60
7 purchase totals =	$967.86		$1,035.3226	$1,035.32	$1,035.35	$1,035.30