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	$205.30	12.181%	$230.3076	$230.31	$230.30	$230.30
Purchase #2	$56.55	11.340%	$62.9628	$62.96	$62.95	$63.00
Purchase #3	$175.52	7.837%	$189.2755	$189.28	$189.30	$189.30
Purchase #4	$71.40	9.692%	$78.3201	$78.32	$78.30	$78.30
Purchase #5	$98.92	6.872%	$105.7178	$105.72	$105.70	$105.70
Purchase #6	$240.67	8.528%	$261.1943	$261.19	$261.20	$261.20
Purchase #7	$73.29	4.124%	$76.3125	$76.31	$76.30	$76.30
7 purchase totals =	$921.65		$1,004.0906	$1,004.09	$1,004.05	$1,004.10