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	$185.33	13.249%	$209.8844	$209.88	$209.90	$209.90
Purchase #2	$230.46	6.454%	$245.3339	$245.33	$245.35	$245.30
Purchase #3	$77.57	5.562%	$81.8844	$81.88	$81.90	$81.90
Purchase #4	$12.41	4.314%	$12.9454	$12.95	$12.95	$12.90
Purchase #5	$162.29	7.856%	$175.0395	$175.04	$175.05	$175.00
Purchase #6	$70.62	6.754%	$75.3897	$75.39	$75.40	$75.40
Purchase #7	$187.45	4.594%	$196.0615	$196.06	$196.05	$196.10
7 purchase totals =	$926.13		$996.5388	$996.53	$996.60	$996.50