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	$223.41	7.676%	$240.559	$240.56	$240.55	$240.60
Purchase #2	$78.32	7.127%	$83.9019	$83.90	$83.90	$83.90
Purchase #3	$119.72	3.320%	$123.6947	$123.69	$123.70	$123.70
Purchase #4	$52.90	12.713%	$59.6252	$59.63	$59.65	$59.60
Purchase #5	$46.82	13.856%	$53.3074	$53.31	$53.30	$53.30
Purchase #6	$177.40	8.110%	$191.7871	$191.79	$191.80	$191.80
Purchase #7	$14.99	8.210%	$16.2207	$16.22	$16.20	$16.20
7 purchase totals =	$713.56		$769.0960	$769.10	$769.10	$769.10