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	$57.89	8.591%	$62.8633	$62.86	$62.85	$62.90
Purchase #2	$178.77	4.124%	$186.1425	$186.14	$186.15	$186.10
Purchase #3	$88.88	4.409%	$92.7987	$92.80	$92.80	$92.80
Purchase #4	$62.49	13.853%	$71.1467	$71.15	$71.15	$71.10
Purchase #5	$161.91	10.522%	$178.9462	$178.95	$178.95	$178.90
Purchase #6	$78.33	4.294%	$81.6935	$81.69	$81.70	$81.70
Purchase #7	$105.75	3.511%	$109.4629	$109.46	$109.45	$109.50
7 purchase totals =	$734.02		$783.0538	$783.05	$783.05	$783.00