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	$53.92	9.498%	$59.0413	$59.04	$59.05	$59.00
Purchase #2	$218.61	6.530%	$232.8852	$232.89	$232.90	$232.90
Purchase #3	$153.77	8.152%	$166.3053	$166.31	$166.30	$166.30
Purchase #4	$123.41	4.384%	$128.8203	$128.82	$128.80	$128.80
Purchase #5	$189.54	13.175%	$214.5119	$214.51	$214.50	$214.50
Purchase #6	$139.32	4.602%	$145.7315	$145.73	$145.75	$145.70
Purchase #7	$215.72	11.215%	$239.913	$239.91	$239.90	$239.90
7 purchase totals =	$1,094.29		$1,187.2085	$1,187.21	$1,187.20	$1,187.10