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	$228.75	6.381%	$243.3465	$243.35	$243.35	$243.30
Purchase #2	$239.30	13.416%	$271.4045	$271.40	$271.40	$271.40
Purchase #3	$25.93	13.415%	$29.4085	$29.41	$29.40	$29.40
Purchase #4	$229.96	5.774%	$243.2379	$243.24	$243.25	$243.20
Purchase #5	$20.28	8.842%	$22.0732	$22.07	$22.05	$22.10
Purchase #6	$105.69	5.741%	$111.7577	$111.76	$111.75	$111.80
Purchase #7	$206.31	7.783%	$222.3671	$222.37	$222.35	$222.40
7 purchase totals =	$1,056.22		$1,143.5954	$1,143.60	$1,143.55	$1,143.60