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	$58.53	7.429%	$62.8782	$62.88	$62.90	$62.90
Purchase #2	$129.69	6.345%	$137.9188	$137.92	$137.90	$137.90
Purchase #3	$151.39	10.800%	$167.7401	$167.74	$167.75	$167.70
Purchase #4	$234.46	10.385%	$258.8087	$258.81	$258.80	$258.80
Purchase #5	$167.79	3.774%	$174.1224	$174.12	$174.10	$174.10
Purchase #6	$99.77	4.356%	$104.116	$104.12	$104.10	$104.10
Purchase #7	$212.50	12.382%	$238.8118	$238.81	$238.80	$238.80
7 purchase totals =	$1,054.13		$1,144.3960	$1,144.40	$1,144.35	$1,144.30