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	$242.91	8.298%	$263.0667	$263.07	$263.05	$263.10
Purchase #2	$31.65	6.787%	$33.7981	$33.80	$33.80	$33.80
Purchase #3	$78.31	3.520%	$81.0665	$81.07	$81.05	$81.10
Purchase #4	$75.59	8.592%	$82.0847	$82.08	$82.10	$82.10
Purchase #5	$123.88	13.731%	$140.89	$140.89	$140.90	$140.90
Purchase #6	$181.54	3.538%	$187.9629	$187.96	$187.95	$188.00
Purchase #7	$38.41	5.735%	$40.6128	$40.61	$40.60	$40.60
7 purchase totals =	$772.29		$829.4817	$829.48	$829.45	$829.60