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	$105.84	9.214%	$115.5921	$115.59	$115.60	$115.60
Purchase #2	$242.77	9.208%	$265.1243	$265.12	$265.10	$265.10
Purchase #3	$65.47	12.749%	$73.8168	$73.82	$73.80	$73.80
Purchase #4	$145.53	4.376%	$151.8984	$151.90	$151.90	$151.90
Purchase #5	$77.94	9.798%	$85.5766	$85.58	$85.60	$85.60
Purchase #6	$162.57	13.404%	$184.3609	$184.36	$184.35	$184.40
Purchase #7	$240.98	12.431%	$270.9362	$270.94	$270.95	$270.90
7 purchase totals =	$1,041.10		$1,147.3053	$1,147.31	$1,147.30	$1,147.30