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	$56.57	5.726%	$59.8092	$59.81	$59.80	$59.80
Purchase #2	$188.26	13.817%	$214.2719	$214.27	$214.25	$214.30
Purchase #3	$109.48	6.822%	$116.9487	$116.95	$116.95	$116.90
Purchase #4	$127.97	9.745%	$140.4407	$140.44	$140.45	$140.40
Purchase #5	$152.83	9.823%	$167.8425	$167.84	$167.85	$167.80
Purchase #6	$104.88	5.464%	$110.6106	$110.61	$110.60	$110.60
Purchase #7	$229.83	5.484%	$242.4339	$242.43	$242.45	$242.40
7 purchase totals =	$969.82		$1,052.3575	$1,052.35	$1,052.35	$1,052.20