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	$90.70	7.391%	$97.4036	$97.40	$97.40	$97.40
Purchase #2	$142.27	9.323%	$155.5338	$155.53	$155.55	$155.50
Purchase #3	$101.47	4.185%	$105.7165	$105.72	$105.70	$105.70
Purchase #4	$53.60	11.418%	$59.72	$59.72	$59.70	$59.70
Purchase #5	$36.48	11.583%	$40.7055	$40.71	$40.70	$40.70
Purchase #6	$55.40	7.592%	$59.606	$59.61	$59.60	$59.60
Purchase #7	$162.36	8.517%	$176.1882	$176.19	$176.20	$176.20
7 purchase totals =	$642.28		$694.8736	$694.88	$694.85	$694.80