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	$207.84	4.484%	$217.1595	$217.16	$217.15	$217.20
Purchase #2	$37.65	7.293%	$40.3958	$40.40	$40.40	$40.40
Purchase #3	$93.62	4.294%	$97.64	$97.64	$97.65	$97.60
Purchase #4	$72.58	8.522%	$78.7653	$78.77	$78.75	$78.80
Purchase #5	$120.31	5.791%	$127.2772	$127.28	$127.30	$127.30
Purchase #6	$206.71	6.145%	$219.4123	$219.41	$219.40	$219.40
Purchase #7	$126.25	12.593%	$142.1487	$142.15	$142.15	$142.10
7 purchase totals =	$864.96		$922.7988	$922.81	$922.80	$922.80