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	$157.97	10.391%	$174.3847	$174.38	$174.40	$174.40
Purchase #2	$38.35	12.839%	$43.2738	$43.27	$43.25	$43.30
Purchase #3	$41.43	10.442%	$45.7561	$45.76	$45.75	$45.80
Purchase #4	$98.81	9.822%	$108.5151	$108.52	$108.50	$108.50
Purchase #5	$67.71	13.583%	$76.907	$76.91	$76.90	$76.90
Purchase #6	$111.27	8.113%	$120.2973	$120.30	$120.30	$120.30
Purchase #7	$102.72	11.835%	$114.8769	$114.88	$114.90	$114.90
7 purchase totals =	$618.26		$684.0109	$684.02	$684.00	$684.10