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	$100.41	5.127%	$105.558	$105.56	$105.55	$105.60
Purchase #2	$131.63	10.577%	$145.5525	$145.55	$145.55	$145.60
Purchase #3	$232.33	9.501%	$254.4037	$254.40	$254.40	$254.40
Purchase #4	$128.93	8.577%	$139.9883	$139.99	$140.00	$140.00
Purchase #5	$198.41	13.835%	$225.86	$225.86	$225.85	$225.90
Purchase #6	$64.91	4.585%	$67.8861	$67.89	$67.90	$67.90
Purchase #7	$9.74	11.644%	$10.8741	$10.87	$10.85	$10.90
7 purchase totals =	$866.36		$950.1227	$950.12	$950.10	$950.30