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	$233.94	13.324%	$265.1102	$265.11	$265.10	$265.10
Purchase #2	$169.56	10.216%	$186.8822	$186.88	$186.90	$186.90
Purchase #3	$44.45	13.505%	$50.453	$50.45	$50.45	$50.50
Purchase #4	$39.40	7.566%	$42.381	$42.38	$42.40	$42.40
Purchase #5	$188.56	12.370%	$211.8849	$211.88	$211.90	$211.90
Purchase #6	$154.28	11.568%	$172.1271	$172.13	$172.15	$172.10
Purchase #7	$181.34	9.451%	$198.4784	$198.48	$198.50	$198.50
7 purchase totals =	$1,011.53		$1,127.3168	$1,127.31	$1,127.40	$1,127.40