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	$98.34	7.584%	$105.7981	$105.80	$105.80	$105.80
Purchase #2	$175.26	9.353%	$191.6521	$191.65	$191.65	$191.70
Purchase #3	$148.52	13.159%	$168.0637	$168.06	$168.05	$168.10
Purchase #4	$206.89	10.606%	$228.8328	$228.83	$228.85	$228.80
Purchase #5	$233.40	7.399%	$250.6693	$250.67	$250.65	$250.70
Purchase #6	$66.82	13.739%	$76.0004	$76.00	$76.00	$76.00
Purchase #7	$85.62	5.357%	$90.2067	$90.21	$90.20	$90.20
7 purchase totals =	$1,014.85		$1,111.2231	$1,111.22	$1,111.20	$1,111.30