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	$164.62	4.696%	$172.3506	$172.35	$172.35	$172.40
Purchase #2	$150.72	12.567%	$169.661	$169.66	$169.65	$169.70
Purchase #3	$56.27	6.179%	$59.7469	$59.75	$59.75	$59.70
Purchase #4	$248.37	11.214%	$276.2222	$276.22	$276.20	$276.20
Purchase #5	$98.31	8.615%	$106.7794	$106.78	$106.80	$106.80
Purchase #6	$71.92	9.222%	$78.5525	$78.55	$78.55	$78.60
Purchase #7	$158.38	4.178%	$164.9971	$165.00	$165.00	$165.00
7 purchase totals =	$948.59		$1,028.3097	$1,028.31	$1,028.30	$1,028.40