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	$134.43	5.670%	$142.0522	$142.05	$142.05	$142.10
Purchase #2	$6.87	3.786%	$7.1301	$7.13	$7.15	$7.10
Purchase #3	$33.66	8.691%	$36.5854	$36.59	$36.60	$36.60
Purchase #4	$74.84	3.173%	$77.2147	$77.21	$77.20	$77.20
Purchase #5	$56.41	4.769%	$59.1002	$59.10	$59.10	$59.10
Purchase #6	$11.65	5.396%	$12.2786	$12.28	$12.30	$12.30
Purchase #7	$89.43	11.785%	$99.9693	$99.97	$99.95	$100.00
7 purchase totals =	$407.29		$434.3305	$434.33	$434.35	$434.40