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	$48.96	7.386%	$52.5762	$52.58	$52.60	$52.60
Purchase #2	$158.66	4.310%	$165.4982	$165.50	$165.50	$165.50
Purchase #3	$26.44	5.522%	$27.9	$27.90	$27.90	$27.90
Purchase #4	$199.29	11.574%	$222.3558	$222.36	$222.35	$222.40
Purchase #5	$230.69	5.354%	$243.0411	$243.04	$243.05	$243.00
Purchase #6	$179.73	4.130%	$187.1528	$187.15	$187.15	$187.20
Purchase #7	$170.49	9.867%	$187.3122	$187.31	$187.30	$187.30
7 purchase totals =	$1,014.26		$1,085.8363	$1,085.84	$1,085.85	$1,085.90