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	$54.78	13.709%	$62.2898	$62.29	$62.30	$62.30
Purchase #2	$117.41	8.683%	$127.6047	$127.60	$127.60	$127.60
Purchase #3	$81.27	6.394%	$86.4664	$86.47	$86.45	$86.50
Purchase #4	$139.81	8.242%	$151.3331	$151.33	$151.35	$151.30
Purchase #5	$151.26	5.732%	$159.9302	$159.93	$159.95	$159.90
Purchase #6	$243.26	10.299%	$268.3133	$268.31	$268.30	$268.30
Purchase #7	$237.49	4.824%	$248.9465	$248.95	$248.95	$248.90
7 purchase totals =	$1,025.28		$1,104.8840	$1,104.88	$1,104.90	$1,104.80