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	$81.34	6.120%	$86.318	$86.32	$86.30	$86.30
Purchase #2	$96.89	10.536%	$107.0983	$107.10	$107.10	$107.10
Purchase #3	$208.55	8.805%	$226.9128	$226.91	$226.90	$226.90
Purchase #4	$28.41	3.868%	$29.5089	$29.51	$29.50	$29.50
Purchase #5	$243.79	11.294%	$271.3236	$271.32	$271.30	$271.30
Purchase #6	$240.83	3.859%	$250.1236	$250.12	$250.10	$250.10
Purchase #7	$100.63	9.142%	$109.8296	$109.83	$109.85	$109.80
7 purchase totals =	$1,000.44		$1,081.1148	$1,081.11	$1,081.05	$1,081.00