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	$183.41	13.250%	$207.7118	$207.71	$207.70	$207.70
Purchase #2	$40.99	7.114%	$43.906	$43.91	$43.90	$43.90
Purchase #3	$209.39	13.772%	$238.2272	$238.23	$238.25	$238.20
Purchase #4	$165.38	6.332%	$175.8519	$175.85	$175.85	$175.90
Purchase #5	$143.54	9.780%	$157.5782	$157.58	$157.60	$157.60
Purchase #6	$52.65	12.382%	$59.1691	$59.17	$59.15	$59.20
Purchase #7	$122.75	11.485%	$136.8478	$136.85	$136.85	$136.80
7 purchase totals =	$918.11		$1,019.2920	$1,019.30	$1,019.30	$1,019.30