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	$160.60	4.192%	$167.3324	$167.33	$167.35	$167.30
Purchase #2	$249.79	6.282%	$265.4818	$265.48	$265.50	$265.50
Purchase #3	$6.48	10.661%	$7.1708	$7.17	$7.15	$7.20
Purchase #4	$214.53	11.584%	$239.3812	$239.38	$239.40	$239.40
Purchase #5	$167.72	11.578%	$187.1386	$187.14	$187.15	$187.10
Purchase #6	$28.43	11.225%	$31.6213	$31.62	$31.60	$31.60
Purchase #7	$239.51	3.614%	$248.1659	$248.17	$248.15	$248.20
7 purchase totals =	$1,067.06		$1,146.2920	$1,146.29	$1,146.30	$1,146.30