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	$53.42	4.280%	$55.7064	$55.71	$55.70	$55.70
Purchase #2	$56.81	10.216%	$62.6137	$62.61	$62.60	$62.60
Purchase #3	$86.46	3.462%	$89.4532	$89.45	$89.45	$89.50
Purchase #4	$106.53	11.682%	$118.9748	$118.97	$118.95	$119.00
Purchase #5	$236.99	10.718%	$262.3906	$262.39	$262.40	$262.40
Purchase #6	$70.54	4.398%	$73.6423	$73.64	$73.65	$73.60
Purchase #7	$170.39	8.478%	$184.8357	$184.84	$184.85	$184.80
7 purchase totals =	$781.14		$847.6167	$847.61	$847.60	$847.60