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	$108.45	10.451%	$119.7841	$119.78	$119.80	$119.80
Purchase #2	$51.89	4.540%	$54.2458	$54.25	$54.25	$54.20
Purchase #3	$245.52	10.279%	$270.757	$270.76	$270.75	$270.80
Purchase #4	$237.26	10.558%	$262.3099	$262.31	$262.30	$262.30
Purchase #5	$44.65	13.738%	$50.784	$50.78	$50.80	$50.80
Purchase #6	$71.98	8.331%	$77.9767	$77.98	$78.00	$78.00
Purchase #7	$170.80	8.616%	$185.5161	$185.52	$185.50	$185.50
7 purchase totals =	$930.55		$1,021.3736	$1,021.38	$1,021.40	$1,021.40