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	$67.87	5.275%	$71.4501	$71.45	$71.45	$71.50
Purchase #2	$208.28	4.738%	$218.1483	$218.15	$218.15	$218.10
Purchase #3	$147.65	13.669%	$167.8323	$167.83	$167.85	$167.80
Purchase #4	$238.78	4.618%	$249.8069	$249.81	$249.80	$249.80
Purchase #5	$218.73	12.216%	$245.4501	$245.45	$245.45	$245.50
Purchase #6	$201.27	10.473%	$222.349	$222.35	$222.35	$222.30
Purchase #7	$203.69	12.248%	$228.638	$228.64	$228.65	$228.60
7 purchase totals =	$1,286.27		$1,403.6747	$1,403.68	$1,403.70	$1,403.60