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	$166.84	11.410%	$185.8764	$185.88	$185.90	$185.90
Purchase #2	$178.50	6.671%	$190.4077	$190.41	$190.40	$190.40
Purchase #3	$53.90	9.868%	$59.2189	$59.22	$59.20	$59.20
Purchase #4	$195.33	8.716%	$212.355	$212.36	$212.35	$212.40
Purchase #5	$185.83	12.522%	$209.0996	$209.10	$209.10	$209.10
Purchase #6	$224.89	4.163%	$234.2522	$234.25	$234.25	$234.30
Purchase #7	$189.66	7.233%	$203.3781	$203.38	$203.40	$203.40
7 purchase totals =	$1,194.95		$1,294.5879	$1,294.60	$1,294.60	$1,294.70