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	$56.57	9.739%	$62.0794	$62.08	$62.10	$62.10
Purchase #2	$140.91	13.666%	$160.1668	$160.17	$160.15	$160.20
Purchase #3	$179.45	5.114%	$188.6271	$188.63	$188.65	$188.60
Purchase #4	$113.97	12.192%	$127.8652	$127.87	$127.85	$127.90
Purchase #5	$100.63	3.514%	$104.1661	$104.17	$104.15	$104.20
Purchase #6	$157.63	6.791%	$168.3347	$168.33	$168.35	$168.30
Purchase #7	$104.72	8.668%	$113.7971	$113.80	$113.80	$113.80
7 purchase totals =	$853.88		$925.0364	$925.05	$925.05	$925.10