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	$53.93	6.796%	$57.5951	$57.60	$57.60	$57.60
Purchase #2	$98.39	12.263%	$110.4556	$110.46	$110.45	$110.50
Purchase #3	$199.75	3.425%	$206.5914	$206.59	$206.60	$206.60
Purchase #4	$197.37	11.745%	$220.5511	$220.55	$220.55	$220.60
Purchase #5	$200.91	7.806%	$216.593	$216.59	$216.60	$216.60
Purchase #6	$58.63	6.523%	$62.4544	$62.45	$62.45	$62.50
Purchase #7	$141.46	6.841%	$151.1373	$151.14	$151.15	$151.10
7 purchase totals =	$950.44		$1,025.3779	$1,025.38	$1,025.40	$1,025.50