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	$76.98	13.405%	$87.2992	$87.30	$87.30	$87.30
Purchase #2	$145.59	11.825%	$162.806	$162.81	$162.80	$162.80
Purchase #3	$230.85	6.418%	$245.666	$245.67	$245.65	$245.70
Purchase #4	$60.90	5.487%	$64.2416	$64.24	$64.25	$64.20
Purchase #5	$78.39	3.151%	$80.8601	$80.86	$80.85	$80.90
Purchase #6	$149.45	7.269%	$160.3135	$160.31	$160.30	$160.30
Purchase #7	$247.37	13.404%	$280.5275	$280.53	$280.55	$280.50
7 purchase totals =	$989.53		$1,081.7139	$1,081.72	$1,081.70	$1,081.70