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	$200.51	6.424%	$213.3908	$213.39	$213.40	$213.40
Purchase #2	$65.88	9.370%	$72.053	$72.05	$72.05	$72.10
Purchase #3	$90.33	12.871%	$101.9564	$101.96	$101.95	$102.00
Purchase #4	$36.49	13.266%	$41.3308	$41.33	$41.35	$41.30
Purchase #5	$69.73	11.743%	$77.9184	$77.92	$77.90	$77.90
Purchase #6	$188.29	6.222%	$200.0054	$200.01	$200.00	$200.00
Purchase #7	$145.31	4.686%	$152.1192	$152.12	$152.10	$152.10
7 purchase totals =	$796.54		$858.7740	$858.78	$858.75	$858.80