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	$213.38	8.663%	$231.8651	$231.87	$231.85	$231.90
Purchase #2	$35.78	6.415%	$38.0753	$38.08	$38.10	$38.10
Purchase #3	$6.88	7.231%	$7.3775	$7.38	$7.40	$7.40
Purchase #4	$94.65	4.148%	$98.5761	$98.58	$98.60	$98.60
Purchase #5	$39.96	12.709%	$45.0385	$45.04	$45.05	$45.00
Purchase #6	$38.37	4.400%	$40.0583	$40.06	$40.05	$40.10
Purchase #7	$111.86	7.769%	$120.5504	$120.55	$120.55	$120.60
7 purchase totals =	$540.88		$581.5412	$581.56	$581.60	$581.70