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	$52.34	11.514%	$58.3664	$58.37	$58.35	$58.40
Purchase #2	$193.38	10.275%	$213.2498	$213.25	$213.25	$213.20
Purchase #3	$227.85	11.229%	$253.4353	$253.44	$253.45	$253.40
Purchase #4	$55.27	7.861%	$59.6148	$59.61	$59.60	$59.60
Purchase #5	$43.74	8.282%	$47.3625	$47.36	$47.35	$47.40
Purchase #6	$222.85	7.791%	$240.2122	$240.21	$240.20	$240.20
Purchase #7	$212.48	11.499%	$236.9131	$236.91	$236.90	$236.90
7 purchase totals =	$1,007.91		$1,109.1541	$1,109.15	$1,109.10	$1,109.10