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	$106.31	4.641%	$111.2438	$111.24	$111.25	$111.20
Purchase #2	$134.28	13.695%	$152.6696	$152.67	$152.65	$152.70
Purchase #3	$93.80	5.744%	$99.1879	$99.19	$99.20	$99.20
Purchase #4	$109.75	5.621%	$115.919	$115.92	$115.90	$115.90
Purchase #5	$126.46	7.605%	$136.0773	$136.08	$136.10	$136.10
Purchase #6	$181.93	8.121%	$196.7045	$196.70	$196.70	$196.70
Purchase #7	$161.40	11.475%	$179.9207	$179.92	$179.90	$179.90
7 purchase totals =	$913.93		$991.7228	$991.72	$991.70	$991.70