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	$47.59	9.595%	$52.1563	$52.16	$52.15	$52.20
Purchase #2	$85.96	4.605%	$89.9185	$89.92	$89.90	$89.90
Purchase #3	$92.60	3.427%	$95.7734	$95.77	$95.75	$95.80
Purchase #4	$17.77	7.295%	$19.0663	$19.07	$19.05	$19.10
Purchase #5	$43.65	3.395%	$45.1319	$45.13	$45.15	$45.10
Purchase #6	$101.39	8.647%	$110.1572	$110.16	$110.15	$110.20
Purchase #7	$28.88	7.345%	$31.0012	$31.00	$31.00	$31.00
7 purchase totals =	$417.84		$443.2048	$443.21	$443.15	$443.30