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	$80.38	9.794%	$88.2524	$88.25	$88.25	$88.30
Purchase #2	$41.34	7.697%	$44.5219	$44.52	$44.50	$44.50
Purchase #3	$121.38	8.674%	$131.9085	$131.91	$131.90	$131.90
Purchase #4	$95.83	8.407%	$103.8864	$103.89	$103.90	$103.90
Purchase #5	$44.26	11.229%	$49.23	$49.23	$49.25	$49.20
Purchase #6	$55.64	10.417%	$61.436	$61.44	$61.45	$61.40
Purchase #7	$59.71	8.260%	$64.642	$64.64	$64.65	$64.60
7 purchase totals =	$498.54		$543.8772	$543.88	$543.90	$543.80