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	$71.76	9.206%	$78.3662	$78.37	$78.35	$78.40
Purchase #2	$212.72	4.443%	$222.1711	$222.17	$222.15	$222.20
Purchase #3	$168.65	5.764%	$178.371	$178.37	$178.35	$178.40
Purchase #4	$234.63	4.783%	$245.8524	$245.85	$245.85	$245.90
Purchase #5	$66.57	8.314%	$72.1046	$72.10	$72.10	$72.10
Purchase #6	$36.29	9.869%	$39.8715	$39.87	$39.85	$39.90
Purchase #7	$234.84	6.596%	$250.33	$250.33	$250.35	$250.30
7 purchase totals =	$1,025.46		$1,087.0668	$1,087.06	$1,087.00	$1,087.20