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	$160.55	13.334%	$181.9577	$181.96	$181.95	$182.00
Purchase #2	$214.67	9.753%	$235.6068	$235.61	$235.60	$235.60
Purchase #3	$225.62	4.314%	$235.3532	$235.35	$235.35	$235.40
Purchase #4	$55.94	6.140%	$59.3747	$59.37	$59.35	$59.40
Purchase #5	$140.39	9.773%	$154.1103	$154.11	$154.10	$154.10
Purchase #6	$64.80	9.726%	$71.1024	$71.10	$71.10	$71.10
Purchase #7	$149.64	11.131%	$166.2964	$166.30	$166.30	$166.30
7 purchase totals =	$1,011.61		$1,103.8015	$1,103.80	$1,103.75	$1,103.90