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	$95.84	3.123%	$98.8331	$98.83	$98.85	$98.80
Purchase #2	$181.62	5.345%	$191.3276	$191.33	$191.35	$191.30
Purchase #3	$175.33	9.490%	$191.9688	$191.97	$191.95	$192.00
Purchase #4	$82.61	12.565%	$92.9899	$92.99	$93.00	$93.00
Purchase #5	$242.91	13.797%	$276.4243	$276.42	$276.40	$276.40
Purchase #6	$40.58	5.606%	$42.8549	$42.85	$42.85	$42.90
Purchase #7	$147.39	11.601%	$164.4887	$164.49	$164.50	$164.50
7 purchase totals =	$966.28		$1,058.8873	$1,058.88	$1,058.90	$1,058.90