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	$177.76	11.542%	$198.2771	$198.28	$198.30	$198.30
Purchase #2	$49.70	6.233%	$52.7978	$52.80	$52.80	$52.80
Purchase #3	$59.36	13.460%	$67.3499	$67.35	$67.35	$67.30
Purchase #4	$200.41	11.731%	$223.9201	$223.92	$223.90	$223.90
Purchase #5	$39.36	5.721%	$41.6118	$41.61	$41.60	$41.60
Purchase #6	$31.26	3.103%	$32.23	$32.23	$32.25	$32.20
Purchase #7	$151.58	10.240%	$167.1018	$167.10	$167.10	$167.10
7 purchase totals =	$709.43		$783.2885	$783.29	$783.30	$783.20