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	$177.40	10.166%	$195.4345	$195.43	$195.45	$195.40
Purchase #2	$77.31	6.823%	$82.5849	$82.58	$82.60	$82.60
Purchase #3	$235.29	10.874%	$260.8754	$260.88	$260.90	$260.90
Purchase #4	$120.62	5.471%	$127.2191	$127.22	$127.20	$127.20
Purchase #5	$239.31	4.154%	$249.2509	$249.25	$249.25	$249.30
Purchase #6	$32.91	3.804%	$34.1619	$34.16	$34.15	$34.20
Purchase #7	$173.45	10.190%	$191.1246	$191.12	$191.10	$191.10
7 purchase totals =	$1,056.29		$1,140.6513	$1,140.64	$1,140.65	$1,140.70