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	$218.33	4.166%	$227.4256	$227.43	$227.45	$227.40
Purchase #2	$37.75	12.743%	$42.5605	$42.56	$42.55	$42.60
Purchase #3	$62.57	9.513%	$68.5223	$68.52	$68.50	$68.50
Purchase #4	$237.43	3.381%	$245.4575	$245.46	$245.45	$245.50
Purchase #5	$83.46	6.398%	$88.7998	$88.80	$88.80	$88.80
Purchase #6	$38.46	6.494%	$40.9576	$40.96	$40.95	$41.00
Purchase #7	$109.55	12.297%	$123.0214	$123.02	$123.00	$123.00
7 purchase totals =	$787.55		$836.7447	$836.75	$836.70	$836.80