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	$225.77	7.826%	$243.4388	$243.44	$243.45	$243.40
Purchase #2	$174.51	11.216%	$194.083	$194.08	$194.10	$194.10
Purchase #3	$36.61	11.657%	$40.8776	$40.88	$40.90	$40.90
Purchase #4	$114.84	10.161%	$126.5089	$126.51	$126.50	$126.50
Purchase #5	$106.91	11.722%	$119.442	$119.44	$119.45	$119.40
Purchase #6	$119.95	3.263%	$123.864	$123.86	$123.85	$123.90
Purchase #7	$53.56	5.111%	$56.2975	$56.30	$56.30	$56.30
7 purchase totals =	$832.15		$904.5118	$904.51	$904.55	$904.50