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	$36.78	9.772%	$40.3741	$40.37	$40.35	$40.40
Purchase #2	$191.54	12.620%	$215.7123	$215.71	$215.70	$215.70
Purchase #3	$131.42	8.746%	$142.914	$142.91	$142.90	$142.90
Purchase #4	$59.41	8.301%	$64.3416	$64.34	$64.35	$64.30
Purchase #5	$190.71	4.515%	$199.3206	$199.32	$199.30	$199.30
Purchase #6	$204.30	13.538%	$231.9581	$231.96	$231.95	$232.00
Purchase #7	$121.67	4.833%	$127.5503	$127.55	$127.55	$127.60
7 purchase totals =	$935.83		$1,022.1710	$1,022.16	$1,022.10	$1,022.20