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	$122.87	4.555%	$128.4667	$128.47	$128.45	$128.50
Purchase #2	$36.83	13.859%	$41.9343	$41.93	$41.95	$41.90
Purchase #3	$46.31	12.460%	$52.0802	$52.08	$52.10	$52.10
Purchase #4	$127.65	4.627%	$133.5564	$133.56	$133.55	$133.60
Purchase #5	$163.64	13.243%	$185.3108	$185.31	$185.30	$185.30
Purchase #6	$229.49	11.686%	$256.3082	$256.31	$256.30	$256.30
Purchase #7	$204.93	12.746%	$231.0504	$231.05	$231.05	$231.10
7 purchase totals =	$931.72		$1,028.7070	$1,028.71	$1,028.70	$1,028.80