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	$195.30	13.687%	$222.0307	$222.03	$222.05	$222.00
Purchase #2	$75.38	13.166%	$85.3045	$85.30	$85.30	$85.30
Purchase #3	$91.33	10.573%	$100.9863	$100.99	$101.00	$101.00
Purchase #4	$112.91	12.643%	$127.1852	$127.19	$127.20	$127.20
Purchase #5	$177.71	10.184%	$195.808	$195.81	$195.80	$195.80
Purchase #6	$126.82	3.429%	$131.1687	$131.17	$131.15	$131.20
Purchase #7	$158.45	4.496%	$165.5739	$165.57	$165.55	$165.60
7 purchase totals =	$937.90		$1,028.0573	$1,028.06	$1,028.05	$1,028.10