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	$42.55	10.634%	$47.0748	$47.07	$47.05	$47.10
Purchase #2	$114.27	12.383%	$128.4201	$128.42	$128.40	$128.40
Purchase #3	$81.48	11.305%	$90.6913	$90.69	$90.70	$90.70
Purchase #4	$201.65	11.679%	$225.2007	$225.20	$225.20	$225.20
Purchase #5	$214.59	4.112%	$223.4139	$223.41	$223.40	$223.40
Purchase #6	$203.86	10.557%	$225.3815	$225.38	$225.40	$225.40
Purchase #7	$78.33	12.808%	$88.3625	$88.36	$88.35	$88.40
7 purchase totals =	$936.73		$1,028.5448	$1,028.53	$1,028.50	$1,028.60