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	$190.41	4.188%	$198.3844	$198.38	$198.40	$198.40
Purchase #2	$127.63	5.679%	$134.8781	$134.88	$134.90	$134.90
Purchase #3	$68.42	4.417%	$71.4421	$71.44	$71.45	$71.40
Purchase #4	$195.29	9.663%	$214.1609	$214.16	$214.15	$214.20
Purchase #5	$89.53	12.577%	$100.7902	$100.79	$100.80	$100.80
Purchase #6	$162.39	5.269%	$170.9463	$170.95	$170.95	$170.90
Purchase #7	$48.30	10.307%	$53.2783	$53.28	$53.30	$53.30
7 purchase totals =	$881.97		$943.8803	$943.88	$943.95	$943.90