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	$153.36	9.740%	$168.2973	$168.30	$168.30	$168.30
Purchase #2	$171.25	9.483%	$187.4896	$187.49	$187.50	$187.50
Purchase #3	$25.89	9.627%	$28.3824	$28.38	$28.40	$28.40
Purchase #4	$58.94	13.468%	$66.878	$66.88	$66.90	$66.90
Purchase #5	$243.27	13.547%	$276.2258	$276.23	$276.25	$276.20
Purchase #6	$41.97	8.593%	$45.5765	$45.58	$45.60	$45.60
Purchase #7	$225.67	13.185%	$255.4246	$255.42	$255.40	$255.40
7 purchase totals =	$920.35		$1,028.2742	$1,028.28	$1,028.35	$1,028.30