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	$151.59	10.139%	$166.9597	$166.96	$166.95	$167.00
Purchase #2	$231.70	5.789%	$245.1131	$245.11	$245.10	$245.10
Purchase #3	$60.93	10.289%	$67.1991	$67.20	$67.20	$67.20
Purchase #4	$154.57	8.383%	$167.5276	$167.53	$167.55	$167.50
Purchase #5	$165.85	9.298%	$181.2707	$181.27	$181.25	$181.30
Purchase #6	$33.62	10.119%	$37.022	$37.02	$37.00	$37.00
Purchase #7	$101.86	6.341%	$108.3189	$108.32	$108.30	$108.30
7 purchase totals =	$900.12		$973.4111	$973.41	$973.35	$973.40