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	$146.95	7.697%	$158.2607	$158.26	$158.25	$158.30
Purchase #2	$36.29	10.398%	$40.0634	$40.06	$40.05	$40.10
Purchase #3	$86.78	3.294%	$89.6385	$89.64	$89.65	$89.60
Purchase #4	$229.94	10.482%	$254.0423	$254.04	$254.05	$254.00
Purchase #5	$71.31	3.715%	$73.9592	$73.96	$73.95	$74.00
Purchase #6	$50.71	4.343%	$52.9123	$52.91	$52.90	$52.90
Purchase #7	$130.93	10.632%	$144.8505	$144.85	$144.85	$144.90
7 purchase totals =	$752.91		$813.7269	$813.72	$813.70	$813.80