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	$61.83	8.641%	$67.1727	$67.17	$67.15	$67.20
Purchase #2	$80.92	11.478%	$90.208	$90.21	$90.20	$90.20
Purchase #3	$97.70	11.838%	$109.2657	$109.27	$109.25	$109.30
Purchase #4	$239.50	12.367%	$269.119	$269.12	$269.10	$269.10
Purchase #5	$143.46	7.765%	$154.5997	$154.60	$154.60	$154.60
Purchase #6	$238.90	5.829%	$252.8255	$252.83	$252.85	$252.80
Purchase #7	$52.86	13.744%	$60.1251	$60.13	$60.15	$60.10
7 purchase totals =	$915.17		$1,003.3157	$1,003.33	$1,003.30	$1,003.30