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	$108.93	6.147%	$115.6259	$115.63	$115.65	$115.60
Purchase #2	$10.37	4.724%	$10.8599	$10.86	$10.85	$10.90
Purchase #3	$115.54	10.355%	$127.5042	$127.50	$127.50	$127.50
Purchase #4	$234.86	12.791%	$264.9009	$264.90	$264.90	$264.90
Purchase #5	$41.48	13.830%	$47.2167	$47.22	$47.20	$47.20
Purchase #6	$82.88	9.359%	$90.6367	$90.64	$90.65	$90.60
Purchase #7	$97.52	4.283%	$101.6968	$101.70	$101.70	$101.70
7 purchase totals =	$691.58		$758.4411	$758.45	$758.45	$758.40