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	$192.80	3.865%	$200.2517	$200.25	$200.25	$200.30
Purchase #2	$83.60	10.641%	$92.4959	$92.50	$92.50	$92.50
Purchase #3	$140.36	8.317%	$152.0337	$152.03	$152.05	$152.00
Purchase #4	$60.92	11.302%	$67.8052	$67.81	$67.80	$67.80
Purchase #5	$80.37	11.631%	$89.7178	$89.72	$89.70	$89.70
Purchase #6	$128.32	13.316%	$145.4071	$145.41	$145.40	$145.40
Purchase #7	$214.33	13.779%	$243.8625	$243.86	$243.85	$243.90
7 purchase totals =	$900.70		$991.5739	$991.58	$991.55	$991.60