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	$173.59	10.362%	$191.5774	$191.58	$191.60	$191.60
Purchase #2	$234.92	5.214%	$247.1687	$247.17	$247.15	$247.20
Purchase #3	$168.50	10.522%	$186.2296	$186.23	$186.25	$186.20
Purchase #4	$198.31	12.627%	$223.3506	$223.35	$223.35	$223.40
Purchase #5	$129.56	8.171%	$140.1463	$140.15	$140.15	$140.10
Purchase #6	$63.95	4.531%	$66.8476	$66.85	$66.85	$66.80
Purchase #7	$29.39	11.507%	$32.7719	$32.77	$32.75	$32.80
7 purchase totals =	$998.22		$1,088.0921	$1,088.10	$1,088.10	$1,088.10