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	$7.32	8.402%	$7.935	$7.94	$7.95	$7.90
Purchase #2	$52.60	4.365%	$54.896	$54.90	$54.90	$54.90
Purchase #3	$249.85	5.571%	$263.7691	$263.77	$263.75	$263.80
Purchase #4	$148.49	12.859%	$167.5843	$167.58	$167.60	$167.60
Purchase #5	$26.87	4.444%	$28.0641	$28.06	$28.05	$28.10
Purchase #6	$39.94	6.597%	$42.5748	$42.57	$42.55	$42.60
Purchase #7	$137.91	9.308%	$150.7467	$150.75	$150.75	$150.70
7 purchase totals =	$662.98		$715.5700	$715.57	$715.55	$715.60