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	$195.33	5.347%	$205.7743	$205.77	$205.75	$205.80
Purchase #2	$111.65	3.354%	$115.3947	$115.39	$115.40	$115.40
Purchase #3	$135.77	10.773%	$150.3965	$150.40	$150.40	$150.40
Purchase #4	$49.25	12.526%	$55.4191	$55.42	$55.40	$55.40
Purchase #5	$120.61	5.784%	$127.5861	$127.59	$127.60	$127.60
Purchase #6	$170.95	11.503%	$190.6144	$190.61	$190.60	$190.60
Purchase #7	$134.92	8.115%	$145.8688	$145.87	$145.85	$145.90
7 purchase totals =	$918.48		$991.0539	$991.05	$991.00	$991.10