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	$125.85	9.491%	$137.7944	$137.79	$137.80	$137.80
Purchase #2	$212.46	3.367%	$219.6135	$219.61	$219.60	$219.60
Purchase #3	$237.78	4.606%	$248.7321	$248.73	$248.75	$248.70
Purchase #4	$108.93	11.594%	$121.5593	$121.56	$121.55	$121.60
Purchase #5	$160.34	4.724%	$167.9145	$167.91	$167.90	$167.90
Purchase #6	$166.96	6.649%	$178.0612	$178.06	$178.05	$178.10
Purchase #7	$40.88	4.760%	$42.8259	$42.83	$42.85	$42.80
7 purchase totals =	$1,053.20		$1,116.5009	$1,116.49	$1,116.50	$1,116.50