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	$228.40	4.378%	$238.3994	$238.40	$238.40	$238.40
Purchase #2	$86.51	4.433%	$90.345	$90.35	$90.35	$90.30
Purchase #3	$249.59	8.369%	$270.4782	$270.48	$270.50	$270.50
Purchase #4	$64.27	9.516%	$70.3859	$70.39	$70.40	$70.40
Purchase #5	$157.48	10.207%	$173.554	$173.55	$173.55	$173.60
Purchase #6	$233.86	8.227%	$253.0997	$253.10	$253.10	$253.10
Purchase #7	$69.54	4.790%	$72.871	$72.87	$72.85	$72.90
7 purchase totals =	$1,089.65		$1,169.1332	$1,169.14	$1,169.15	$1,169.20